It is natural for people to fall away from something. If that person has been exposed to soo much of it they become desensitize so they would eventually lose interest in it. Of course it doesn't apply for everyone for example you, assuming you had as much anime as the rest of your friends. If you want them to be an anime fan again like you then you would have to entice them with those rare anime which are actually good unlike the regular crap that are made to fill up time slots.