The problem is that BIK tempts people into the wrong tool for the job. I used to have a 2.0 diesel as a company car. Perfect for hacking up and down the motorway for my job. Then diesels became the work of Satan himself because VW got caught cheating emissions tests.Well they can opt for anything I'd guess, but I am sure they want to pay less BIK tax, so if you see a Tesla Model 3 that costs you £70 per month, or a BMW 320i that costs you £250 per month, it's not a hard choice unless you either love BMW's, or want to spend more?
So then I ended up in a 1.4 petrol when it came to change cars. It's not as good for motorway work and it uses more fuel while doing so.
Then WLTP happened and my colleague had to get a car. He ended up in a 3 cylinder 1.0 petrol to hack up and down the motorway in. He uses about the same amount of fuel as me but has a worse time while doing so.
My next car will be a "worst of both worlds" PHEV. It will almost definitely use more fuel than my current car because I stupidly chased ultimate BIK savings from what was suitable, acceptable to the company and in budget. The right tool for the job is still that 2.0 diesel I had nearly 6 years ago.
It's not much more of a leap to people getting all excited over a brand new EV for the monthly cost of a Burger King meal even though they have no suitable means of charging the thing.
So you are right, there is still choice (in many cases) but people's natural reluctance to give away cash to the tax man is one hell of an influencing factor.