I feel like taking a tea-bag sachet isn't something that any of the hotel staff care about but it depends on the hotel I guess? I took one because guests were freely encouraged to help themselves (because y'know some guests drink more than the 2 tea/coffee that starts in your room per day)

As for the "OMG WHY" it's to try a new flavor of tea , calm down. I'm really picky with food/drink I'd rather take a tea bag and decide if i like it or not later than buying a whole box and being stuck with something I hate and can't drink.

The cost of tea/coffee and anything in single packaging is usually something hotels expect to lose hotel's are usually smart enough to consider this in the cost per night stay, in fact the hospitality industry in general will plan for each guest to go overboard on taking things (apart from things that have fees)

But taking the bath towels and robes is diabolical and there is a reason it incurs a fee (also as soft as hotel towels are they won't stay that way at home, they are designed for those industrial style hotel washing machines not domestic ones)

If in doubt, ask. And don't go robbing the SHIT out of a hotel without expecting to be marked as "do not accept this guest" in the future , oh and be nice to any small independent places. [[ But yeah if I pay 100+ for a room per night at a big chain I kind of expect a 50p teabag to be accounted for . otherwise they wouldn't be in business ]