I had a hard time finding a recent thread on this topic, so I don't mind it continuing
Anyway, you asked an interesting question:
I'm curious why people call them 'fursonas' when they're just RP characters!
For me, I've rarely used my fursonas for RP. I have two characters -- Alex, a pink fox, and Digby, the picture in my current avatar. Fursonas are an embodiment of who I am; while I express myself normally IRL, I can create an alternate me online. I mean, I still have elements of myself, but it's a different way to act!
This really is the magic of the fandom. The fursona is an intersection between the imagination and reality -- people can look at Digby and only see the imagination side, but he has become real to me in a sense. Some people online will know me in no other way, and that (though strange) is amazingly real.
But some fursonas are just for RP. That's okay, too