I don't "like" someone without loving them. is this strange?

Starting to realize that when I am sexually attracted to someone, I enjoy spending time with them, we laugh and get along - then I am in love with them. So I always assumed that if I'm having a good time with someone, good sex and good conversation, then they love me too OR have the possibility to fall in love with me.
For me, it doesn't make sense how you can have good chemistry, physical and mentally, with someone and have just a good genuine time with them, how you don't fall in love with them?
If I don't have a good time with someone, they don't stimulate me and I am not excited to see them, then I just don't see them anymore, and I know very very quickly (before or on the first or second date).
So, when you "like" people, do you kind of 'like' them 25%? 50%? 75%? What makes you want to continue seeing them if you aren't having a really good time with them? Why have sex with someone if you don't genuinely value this person? Why date someone if you only like them 50%? isn't that unsatisfying to spend time with someone who only fulfills you just a little bit?
for me, if I am not genuinely excited about them and I feel my time is better spent alone than with them, I don't like them at all and I don't continue to see or talk to them.
Thoughts?