We've been in our new house for about 2 years now. I have noticed every time I change out a bulb, it's for the same one. For example, the ceiling fan has 4 lights. I have replaced the bulb for the same spot 4 times, while the other 3 are the original bulbs from 2 years ago. Same for the vanity lights in the bathroom. Why is that happening and how do we fix it?

I dont know if you can replace the socket on them or not.
I had a single bulb lamp were I had the same issue, and I went down to the home center and bought a socket and wired it up and have had no issues since then.