I’m not sure that is the correct metric to look at. As it is a very very high end product.
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.