DI2 came out in 2001. How many years do you think this 'fad' will last?
https://www.prnewswire.com/news-releases/bicycle-gearbox-sys...
Still growing at a nice rate and every single pro team has been using it for years now.
All I see now around where I live, which is heavily bike centric, are e-bikes...
For the same reason, what the pros do on their rigs is no concern for the 99.9% of mountain bikers.
I wouldn't bring anything I can't repair or troubleshoot directly out in the mountains, let alone anything that can discharge and not work anymore.
Shimano also brought electronic to their 105 line and SRAM has it on Rival. Neither is high end, never mind ultra high end. I’m not a MTBer so I’m not aware of how that market is, but electronic shifting is definitely prevalent in road, gravel and cross.