I wasn't speaking for every person in a w/c, but you come across a bit like OP, a total ray of sun shine.
Life is hard enough, then add in a disability or life's other little treasures and you have the perfect recipe to be grumpy. It's just in my world of pretend unicorns and rainbows, if I was a disabled/chronically ill person who chose to dwell on every little thing I fear my head would explode.
This is exactly why I couldn't get on with the concept of the spoonie community. I don't want to spend my life going oh I feel sick, oh that hurts, yay now I've got reflux, this pain feels like something is going to rupture, my left side is numb, the latter rather amusing as I didn't realise till I tried to stand up and did a groovy little dance to stop me falling yet again. I'm to blame for tummy posts as it's my one pet hate having gastric/bowel issues, now every day some people are going look at my swollen belly. I could shoot myself at times, if I knew I was going to inspire something so annoying.
I want something the opposite of the spoonie culture, where the focus is on positives. On groups you have anyone do anything without an addendum of 'obviously with the help from my carer/family member' when realistically I think they did it alone, but the ready to bake mix would take away from their illness if they admitted to doing something alone.
Like for me a bit grim fair enough, but getting my hair washed and clothes changed would be a big deal. A bit like normal people posts I had a greeeeeat relaxing bath. 
Life is going to be so grim if you're simmering inside most of the time.
I hasten to add again, although someone has used this as an example, imagine if 90 year old Mr Smith comes back to his trolley and its full of packs of rice. He's going to be so upset that some eejit would do this, in his mind for no apparent reason. It's easier for only just mobile Mr Smith to walk and grab the cat biscuits he forget than lugging round his trolley so he left it there, wrongly thinking what is the worst that could happen.
We want to be treated with respect, but if you treat people like this, why should we get one ounce of respect.
To the poorly Mums with kids with health issues too 
I would give you wine but it's only 9am 