(I'm not overly fussed if this outs me)
As a child of a former doctors receptionist, I will tell you why: it's an incredibly stressful job.
I've had to bite my lip the last few years but now she's quit, I can finally say what I've been wanting to say.
I see a lot of comments about the receptionists not being medical professionals when asking the patient what the problem is, 1) they do learn some medical knowledge doing the job and 2) they need to know the problem so they can assess what kind of appointment you need.
Also it's not the receptionists fault if the doctors are running late, please don't have a go at them and likewise with the lack of appointments- this is a nationwide issue, not just subjected to one particularly surgery. I have witnessed a complete and utter cunt being abusive (including threats) to my mum, I really wanted to smack the twat right there in the surgery. My mum has been physically assaulted twice, in the nearly 8 years she was there- why should she be subjected to that for just doing her job?
But it isn't just the patient that causes the stress, it's also the staff. My mum was signed off with stress 3 times, put onto anti-depressants and even had suicidal thoughts, it was awful seeing her like it- it got to the point where she was using her migraines as an excuse not to go in. Her ex-ex boss was a complete arsehole, she had little sympathy or empathy for anyone- my mum suffered from ill health in 2012 resulting in 3 hospital stays (the longest being 11 days) and 2 operations, her ex-ex boss actually rang her whilst she was still in hospital, asking if she'll be back soon whilst recovering from major surgery! Another receptionist is a bully and because her actions, 4 people have quit their jobs.
So this is why they are 'rude' but I'm so glad she is out of that place as we always got the worse end of it (not her fault though).