My theory is, if there's a readily accessible place for trays to go, yes, I'll clear my table.
If there isn't, I make sure everything is piled back on my tray neatly, so nothing will fly off as the person clearing tables walks off with it.
I used to do it as a job when I was 16, so now stack the tray as I liked to do it when I cleared tables.
I didn't mind people not clearing their own stuff away, as our tray racks were in a designated cleaning area that didn't look like it was for customers.
In a way, it's helpful to leave it as if you're out the back and you come back to discover a tray put away, you may not remember exactly which table they were on to go and clean it.
What I hated though were the customers who just assumed that as it was my job, they could leave it in a total shit state with no attempt to being tidy. The worst one I had was a family group of about 10 that came in, moved a load of tables together and then proceeded to let their toddlers smush their food in to every surface within arms reach and throw it all on the floor. When they finished, they literally got up and walked away. It took me about half an hour to clear up their waste then rearrange the furniture and clean it from top to bottom. I always wondered whether they treated their own homes like that.
Sp, from an ex-cafe worker, please just put things back on your tray, stacked neatly, with all food waste on the top plate. If there's something you haven't used, like jam pots or sauce sachets, put them to one end out of the way, as they may be able to be saved.