I never do it for freebies, I have just always liked being able to help people.
Me, I have grown up on the internet, and I have always used forums. Namely, I used "ProBoards" forums, where you can create your own free message board. In this everyone helps one another, be it with graphic design, or coding (it had its own editable coding and design so you could do anything with it).. And there were message boards created entirely for these purposes and for many many other purposes too. So for me, I "got into" the mindset to help anyone if I can, and from there it just continued into real life and on camsites. Note: I started on the message boards from around the age of 14 or 15, so I was still young (these were no adult sites, so don't worry - but it's also how I started to learn and enjoy design/coding). So many people wanted to customize their own message board, so I would create entire themes for them that anyone could use and install. It was such a great experience in terms of learning to share (really the whole "sharing is caring" quote makes sense in places like that).
I will always help people if I am able to, not completely selflessly, of course, by this, I don't mean I want some nudity or whatever in return. What I mean is, as a "whole", one day I may need help with something (something online or in real life) and I would hope that someone would "come to my rescue" and help or give the advice I need.
As an adult, I can understand and appreciate things a lot more, especially when it comes to time and the internet. A lot of models have other jobs, kids, and other duties, so if I can help to save them a headache (I don't have a family to look after so I have more time than a lot) I am no expert for computers or the internet (by far), but I am comfortable, and a lot of models are a bit scared to touch things or to look etc so if I can help them with it, then I am more than happy to.
it's really that simple for me.