I generally give couple bucks

for hotel housekeeping staff.

Those workers (mostly hispanic) work very hard. If they do my room clean, very polite and pleasant, I generally tip them.

This is not a matter of "need" or "no need" - it is up to each individual's standard.

BTW, while shorts are very popular in summer time - if you try to go to some better restaurants, they will not let you in.

How to dress is also a very personal matter - one can dress to ones own liking and ignore what the surrounding environments are, or one can respect where one is and dress appropriately. It is also a personal choice, like tipping.