That is the restaurant's right. I'm fine with it. If a restaurant sells unsweetened decaf tea I will happily pay for. Panera and Tim hortons both offer some nice ones.
Would you rather I eat elsewhere if I can't find a drink on your menu? Or use your lemons to flavor the water? It seems to me some business is better than none. I've only seen signs about outside food at fast food places.
As far as tipping goes, you are right. I can't tell you how many people stiff the wait staff.
I've also asked for a cup of hot water and paid for it. If someone will work with me I am beyond happy. I just can't drink carbonation, choose not to drink sugar that isn't fermented and caffeine after 2 or 3 doesn't work for me.
No, some times "some" business can be bad. Now this is just very very general information, there are always exceptions and alternatives.
A successful restaurant runs on making a certain amount in sales based on a time period, some business set that time in a week, others daily receipts and I know some restuarantuers who calculate hourly what the receipts should look like. Now all businesses have a defined amount of space and guest they can hold.
So if my business has 20 tables, I calculate how much per person I need to bring in. So if I have a booth that can fit 6 people and a young couple comes in and wants to eat in that booth, that's bad. On a spreadsheet that's lost revenue because the space that could be made generating income from 4 or 6 is now generating less. Now once a day, no problem. 10 or 12 times a day. big problem. Have you ever gone into a place with tons of booths empty and you wonder why you can't sit at them and you're asked to wait?
Now if I'm running a chilis or Olive Garden, it may not be a huge issue, corporate may absorb some of that cost but if you're a family business you want the space used to maximum capacity.
Same with parties where there maybe 3 girlfriends but only 1 really orders a dish, they other two just get a drink or folks who split meals. Sure technically that is "some" money but the owner is looking at two seats he possible could be filing with 3 full tabs now being used at a loss. And again, yes once or twice you can recoup. 9 or 10 customers coming in splitting meals can be a big problem. Hence some restuarants charging a split plate fee.
So if a place needs 5K a day to see a profit, simply saying "some money" is better than none is not how it's viewed. That's why you some bartenders hate patrons who "nurse" one beer through an entire football game ( I hate those guys, you want 1 beer, stay home) He's not generating any income and no his 10 bucks is not better than nothing. He's taking up space we want to fill with the guy who's going to buy a round every time a touch down is scored.
It's a quirky business.
Now my family and I are the exact opposite, we don't drink a lot of soda at home so when we go out soda is a "treat" for us. I love a great pizza with a ice cold coke. So when I know I'm going out to eat, the fact is I'm not trying to save money. IMO the way to save money is to not eat out.
Lastly now that most restaurants offer free refills, a glass of soda is not 3 bucks. Most kids will have at least 1 refill each