I tend to agree with the sentiment "if you can't lift it don't expect us to" , but as a 4ft 10 ish person I have severe problems on a lot of commercial jets. I flew recently from LHR to YYZ on AC's new 777 in first class. There is no place to put your bag under the seat in the new suite arrangement (this is my usual solution to the can't reach bin scenario) and I seriously could not reach the overhead bin , my husband was stuck over the other side of the cabin (we didn't realise that although the seats are side by side on the seat map , you can't get to or talk to each other!!) . He had to walk all the way round , through the galley and back up to put it in for me!
Personally I think all carry on baggage should have to fit under the seat , I get very nervous with those heavy bags above my head!
Having said that I also think that planes should be designed so that there is room under the seat .