I see the hassle as more for DIY users than factories. Labor is very cheap in China so the added cost is nominal. I get a Bosh PAS is more expensive but not in the big scheme of things. I bet 90% of the people riding the 99% of ebikes that don't come with a throttle are happy and don't care about having a throttle. I like my throttle for all the reasons you listed but I still don't want a bike without PAS. Best of both worlds I guess.
That is a great point....You are certainly correct about the complexity being more of a DIYer issue than a turnkey factory problem.
My one big issue with torque based PAS (these is the top parameter utilized by all the big motor makers) is that weaker riders sometimes can not put the ebike in an assist mode that provide full power no matter how hard they try. This impacts people with bad knees or handicaps but for average riders they work great. But if I'm installing a kit I have no clue why someone wouldn't just go the easy route and go throttle only (saves money and time and you'll be able to install what you purchased).
I like that Bafang has there new mid drives supporting both PAS and throttle as that is going to take some market share from the bigger motor names. They have been marketing against throttles but my guess is two years from now Bosch, Yamaha, TQ, Brose, etc. will all have a throttle mode option. They'll then claim they were always planning to do this for the US consumer which is total BS but they'll say it anyway (marketing and truthfullness seem to be polar opposites).