ees and ers

Buses usually have notices stating how many passengers can be carried. My imagination is often stimulated by one particular category, the 'standees'

I visualise noble souls lying down in the aisles so that others, the standers, may stand on them.

I've never been able to think of a convincing reason for the standers wanting to do that, or for the standees allowing them to, but I keep puzzling away, hoping for an answer.

Even more puzzling are references to 'attendees' at a meeting. As an attendee must be something that is attended, it must be the meeting itself, but why refer to it with such coy circumlocution?

I suppose that as songs are sung, and cigars are smoked, they could be referred to respectively as 'singees' and 'smokees', but I hope they never will be.

Finally, is 'drinkies' a corruption of 'drinkees' ?