Why is there no 3g video converter freeware while other formats like mp4 can be converted for free?

I've been looking for 3gp converters and they are usually demo versions that I have to get a serial code or an access code for (and some of the codes/serials are really expensive!). I have tried the Quicktime, but it turns out you need the Pro to convert videos to 3gp! Grabe naman! Paano ba yan?