They’re boutique vehicles now because the tech isn’t ready for prime time. But tech improves. Think of modern electric cars like the Audible Player, an early digital audio player. It cost $200 1998 dollars, had a whopping 4MB of storage and 2 hours worth of battery life. But that what we now know of as MP3 players were a doomed technology line, it just means it wasn’t ready yet. 3 years made a big difference in that world, I’m thinking electric cars need more like 10 or even 20.
They’ll grow more and more in capabilities...but as you say, it needs some substantial breakthroughs - in a number of areas. Right now, they are very good in some very limited environments, mediocre in others, and downright ineffective in many common situations.