Why even bother?

I lunch out on Saturdays. A deliberate decision I made a few years back since I hang out with friends and like minded people on Saturdays. (Helps me have an uninterrupted Sunday with my family and loved ones.)
 
Last Saturday I was at this upscale Mexican restaurant in Khan Market with a friend. We ordered chicken breast with some mexican stuff. (Can’t remember the name of the dish, it sounded gibberish. Like most of the things in the menu. I struggle beyond quesadillas, tacos and enchiladas when it comes to mexican cuisine.)
 
The food was delicious! The service was fantastic with touch of fake American accent. (Which I didn’t mind.) They helped us identify the items on the plate. I finished 15 minutes before my friend, who was trying to figure out if the bean sauce went with the nacho or rice. (It didn’t matter. I didn’t give a damn and ate it all!)
 
And then came the bill. As I opened my wallet I noticed a small glitch in the bill. The 6% service tax component was on the total bill instead of the service charge (which can be 5-20% of the total). I called in the manager who said that everyone in the market does the same.
 
Doesn’t make any sense. I placed my argument and pointed out the flawed practice. This was wrong! And while I was at it, I heard this lady (who was sitting on my left) say, “Excuse me. I’m the owner of the restaurant. And he’s right.”
 
I couldn’t help but say, “Well, that doesn’t make things right. Does it? It’s still wrong.” Let me show you something. I pulled out a notification from the state’s high court highlighting the service tax bit. (I’d saved this off of the internet. Didn’t plan to use it though, since I’ve never faced this before.)
 
Upon reading the notice, she shrugged and said, “everyone in Khan Market does the same. Sorry, I was only trying to help. I was wrong.” And then she left the place.
 
Wow! I’m not peeved or upset. But stunned. That’s it! So much for being the owner of the restaurant.
 
What surprises me the most is the argument placed here: a) I’m the owner of the restaurant; b) everyone does the same. Both weak arguments at that. It doesn’t change anything. The practice is still wrong. And I still ended up paying the bill. (It wasn’t a huge amount anyway, I wanted to bring to their attention.)
 
I can’t imagine running a successful business like this. If everyone does it, wouldn’t it make sense for you to question it? Is blind-leading-the-blind the new business strategy?