Auto-Towing - why is this not more popular?

I had an interesting conversation with a pal about auto-tow glider launching method recently. It seems academic really.

When cost is considered, auto-towing has to be far more affordable than even winching. Maybe $1.50 per tow, max? In aviation, the cost is always critical. Especially in gliding club environments. Aerotows are $30-50 per tow. Winches are extremely expensive to purchase, to maintain, and insure and require skilled operators.

Auto-tow procedure seems fairly simple. 1) Steady strong acceleration until the glider comes airborne, then 2) add 5mph and 3) hold that speed until you hear differently from the pilot. Of course, 4) stop at the end of the runway :-).

Why is auto-towing not a mainstream method of getting gliders airborne?

I saw auto-towing happen regularly at Hobbs this year (my first visit). It was quite graceful and almost exotic. To be honest, it looks even more fun than winching.

I am very interested in learning what you know, your thoughts and your opinions.

Sean
7T