The same argument could be made about the flooring forum. Why have a designated forum for floor coatings, why not wall paint, ventilation systems, ceiling treatments, cabinets?
The answer to "why," is that a lift isn't just a tool, it's something that have to design your whole garage around. There are lifts that have to a significant amount of work to install. Say, in the case of an in-ground lift. Or, the modification of a structure to accommodate a lift. There's room to talk about what makers of lifts are best, who to have install them, etc.
On the other side of the forum, there's the benefit of having a lift manufacturer as a sub-forum sponsor. Since there is quite a bit of money in industry, they are always looking for a way to advertise.
I know in the case of my garage-building adventure, it is spawned by the desire to have a lift, and a place to put it. It's the centerpiece, what separates where you park your car, from where you build your car. It's that want of a lift, that drove me to this site in the first place.