Why does restore only do half its job?

Apparently I screwed up my system yesterday. Last night I lost my internet connection and it was still gone this morning. I was able to use me other OS so I knew it was a problem with my installation. I did a system restore. But when I opened firefox I was informed that using my old profile could cause bookmark, etc loss. So I restored my /home folder. I then got the same warning message. I had the option of creating a new profile so I did. But my bookmarks were gone so I then restored bookmarks from a backup file. Same with all my logins. Now everything seems good.
My question is, why was a restore of my /home folder not enough to get firefox running? Why did I need a new profile? Can I now delete my old profile?