Snip-

Apart from initial cost and traditionalism - 'gliders
dont have engines', I
cannot
understand why so few people have SLMG.

Snip

Well I certainly cannot argue with the intial cost
being a drawback, but not sure about the tradionalism.
Besides being expensive, one might consider

1.) Density altitude
2.) Reliability of the engine
3.) Noise(probably more an issue in Europe)

Although improvements are being made, and there seems
to be fewer lawn-mower engines in them, I am most interested
in seeing how the electric-motored versions do.