Why do we consider our customs to be a normal basis? In the end, everything is subjective

I mean not really. Our non-religious customs provide tangible, measurable, real world benefits. I go to the gym because it's healthy and I live with my family because it provides mutual monetary and emotional benefits. I say thanks and sorry because it tells the other person that I appreciate the time and attention they have given me or the inconvenience I have caused them and vice versa. It may be a small thing, but I think it helps with social cohesion and trust to know that others acknowledge those things. It's not just an arbitrary sound I make with my mouth that I was taught to do "because god commands it or else", which no explanation of meaning or benefit.

Those things generally have measurable reasons and benefits behind them. They are fundamentally different than a ritual that I do simply because "God says so" or because if I don't then I will go to hell or whatever. You can say those are logical reasons and benefits as well but they aren't really provable or measurable until after one's death and they don't have any significance if you are a non-believer. I mean no matter what religion you believe in, you can't say exercise isn't healthy.

Sure, I acknowledge that religious rituals may have benefits that seem very real to the person who is practicing them, but generally they are only beneficial if you buy into that whole religion. I also dislike the fact that some of these rituals provide no tangible benefit and simply involve blindly following God's order just for the sake of submission. It's just creepy to me because it reeks of unquestionable authority and indoctrination.