Who clears away at macdonalds but leaves their glass on the table in a pub?
Seems everybody I know leaves their glass on the table even if they have to walk past the bar to leave.
When I was little my dad used to take me to the pub and I used to collect glasses for them. It has stuck and I will usually always take my glass back to the bar.
Since I've worked in a restaurant I will occasionally clear my plates away at cafés and restaurants. Just a simple "where would you like these?" does the job. Or even if you stack them at the table, with all the crap/cutlery on the top plate. So the person can just take it away in one go.
Didn't make my life much more difficult and it makes you feel good.