Why do (some) elderly complain so much?

What @Katypp said.
This belief by the young of today that boomers had "an easier life" than them is getting stale. Every generation has its problems. The elderly are not one homogeneous mass. They are individuals all with different lives and experiences.

Not directed directly at you, but your post sort of sums up the self-obsession so prevalent on MN at the moment.
Yes I imagine this thread is going to go the same way as threads about pensioners always do - greedy boomers, deliberately making life difficult for the eternally-suffering young families.
I find it quite alarming that a lot of younger people are so entrenched in their view that their suffering is worse than any other generation ever that they cannot see that just because their granny's life has (in their view) been easier than theirs, granny must not interupt their busy lives to complain about anything, ever.
You will be old one day. You too will find your world has shrunk. You will lose your friends one-by-one. You will not want to be turfed out of your 'massive' house to make way for suffering young families. You may find you are reluctant to share your 'hoard' of cash in case you need it. And of course, if half of MN gets its way, you won't have a pension because they should be abolished so greedy boomers suffer more than younger generations. I hope your children will be more empathetic than today's 30-somethings are.

I hear you OP. This week alone 3 white male seemingly well groomed 75+ plus patients wanted to and in fact did spend part of their exam time while in the room with me testing/ examining them complaining about the “check in process” at our medical facility. And staff had already empathetically and specifically guided them thru the process altho the patient themselves was rude dismissive argumentative AND condescending all at the same time.

finally like a child I literally put my fingers in my ears and while doing this gesture said…I’m not listening to this anymore. You have wasted 11 minutes of your appt time. Do you want your medical appt to proceed or do you want to leave/ reschedule.

they complain and complain and can’t seem to accept that we the medical staff have no control over the “ system” and simply work in it but did not create it.

Ps was talking to my mum recently and she said it’s awful how nobody listens to you, everyone coos over you and patronises you even though you’ve the same lived experiences as them plus years more!!

You may think they had the best of life but most of them had limited choices. It wasn’t easy for women to work outside the home (in a professional way) a lot had no choice but to marry as getting a mortgage would have been difficult.

My mum is 78. She’s an absolute cow but she’s not had a life I’d have wanted for myself.

I’m only 46, but I’d guess when you’re older, don’t have the freedoms you had previously in getting about, have lost your friends and family don’t come to visit anymore, people act like you may have dementia because you don’t have the same opinions on them (love that on mn, any chance she’s got dementia? because someone said something the op couldn’t empathise with), then the little things probably exhaust you!

Plus as I’ve said I’m only 46, and in the last few years my favourite perfume and mascara have been discontinued and they were two of my joys in life and I’m pissed off!!

Maybe you should rethink your career choice

I think fear for their future looms large for the aging and elderly. Very often, they will have lost their spouse, possibly cared or watched them die.
They are lonely, and fearful for their own end, and they are not wrong to be fearful.
They are no longer employed or feel they are of use to anyone. They are watching their friends and family die. They have their own, possibly life-limiting conditions to deal with, not to speak of reduced mobility...and life can become an effort.
Frankly, old age can be wretched.

Become worn down by declining physical abilities ?

Some however are amazingly cheery, despite being widowed, having lessening mobility..

It’s because they have too much time on their hands. Employed people with children to bring up, do not have the time to think about minor niggles.

They hyper-focus too, won’t rest until something is sorted.

Because their worlds have become smaller, they've probably lost people they love and a lot of their friends, fear - the world has changed hugely in the last 3 or 4 decades, they're maybe scared they'll die soon so they focus on the small things they might still have some control over.
Surely you must have some understanding if you work with the elderly? Or perhaps not.

I had a conversation with my mum (now 75) recently where I recalled what she used to say about visits to my two grannies (her mother and her mother in law) when they were old.

She would say that found them a struggle, because they only wanted to talk about their health woes, and their bunions and constipation and aching backs, and how awful it was being old and tell the same stories again and again from the past.

My mum said that yes she had felt like that back then, but that now she was ancient and her body was betraying her (she’s comparatively extremely health and active for 75!!!) she could see it from their perspective, and could understand why this was all they wanted to talk about. She said I should try to be more empathetic to her than she had been to them and just bloody listen!!!

I think there is probably a lesson in there for her and for me

Are you in the right job?

Maybe because their world has shrunk and so small things to us seem big to them

Perhaps because their health or fitness or life is no longer as they would wish. You can be wealthy and still depressed/unhappy.