Honestly, this is just habit -- it is a learned behavior, and so you need to consciously unlearn it if you want to change it. I grew up in a very frugal family, and we almost never entertained ourselves with things that cost money because we didn't have it to spend. DH grew up in a family with plenty of money, so he learned to spend it freely. After 20+ years of marriage, I too default to "let's go out to dinner/movie/bar" just because I want to get out of the house and do something different. And when I try to think of free things to do, I totally draw a blank.
And yet, I know for a fact that there are free things that can be done and that are satisfying, because I lived that way for 18+ years -- and it's not like I was miserable! I've just gotten lazy and trained myself to do the easy/obvious things, now that I have money to blow on them (and half the time those get boring anyway!).
So if you want to change it, give yourself a very strict "going out" budget, and stick to it. Then spend some of those lazy mornings actively thinking/brainstorming/researching/trying other options -- looking for meetup groups, or checking out whatever free festivals or events your town has, or going out for a bike ride or to the park, or whatever. This will feel uncomfortable -- changing habits always is, and at some point your brain will likely rebel at the constraints. But if you can stick with it, your brain will adjust, and it will re-learn new habits along those more frugal lines.
Tl;dr: Your brain is always going to default to what is easy, what you always do, because that is what you have trained it to think about. Changing that default requires mental discomfort: you need to forcibly close off those "routine" choices in order to force your brain to think about other options. But once you get over the hump, those more frugal options will become the automatic defaults and start feeling "normal."