Hmmm,through axles on the forks yes but trials riding has a major factor which is angles and measurements. We are completely anal about every single degree or mm. If you ran a through-axle on the rear there's really only 2 ways of tensioning the chain. A tensioner which adds weight or something like a eccentric bottom bracket which can essentially raise,lower or even move the BB further back. Essentially this also adds more weight as you have to have a shell in shell. Trials is a fickle thing! The oldest methods seem to be the easiest and reliable. I've seen some mental designs,angles and massive BB heights and trials always comes full circle!
Take for example Fontenoys elephant bike or the Vinco. Crazy bikes! Then everything goes tame and low then boom...back up to +100 again and hydro formed to oblivion!
The markets always kept so fresh this way!
Sorry it's a rant....just finished nightshift and I've a terrible case of exhaustion mouth!