Is AUTHOR wrong in the post ? POST : AITA For not wanting to tip because everyone else expected me to?

Long story short I go out with a group of friends. Every time we go out I’m the only person to tip. So we went out this weekend and when the bill came I only payed for my beers, I was then asked…verbatim “yo, you only paid for your brews, you’re not going to tip?” 

I said “FUCK NO” why am I the only one that has to tip? I always tip every waitress/waiter, bartender and so on why the hell should I have to tip on my own for a whole group? 

It becomes/became an issue for me because when we go out as a group I’m the only one to tip. Everyone else feels and says “I only paid for this, so I shouldn’t tip”  buy they expect me to?

So Reddit AITA for my actions?
Also, regardless of what my group says I always tip 30%. 