I care but in a different way. I feel she has lived life more than me if she has had more partners than me. like more fun. For example this one girl I liked had a threesome with her ex and a girlfriend. But when I met her, she wanted to settle down. But now I wanted a threesome and she is "over" her experimenting days. So now she has had this, I havnt and to be with her I need to give that up? That's where sexual history for me becomes a challenge. Only once I tick off my really massive sexual bucket list, then I probably would get over that jealousy.
I don't care TOO much but I would be lying if I said there's no limit. How many is too many? It depends on how old he is and at what age he started having sex. People often don't take these things into consideration.