(Look at the idjits buying £40k Teslas, thinking that they're getting an income tax break - they've forgotten that they're paying more VAT, import duties, and taxes on car distributors by being induced into buying new motors)
This depends on what the alternative is.
The concept of a company cars on a business lease has been with us for many years now, it's nothing new.
At current, a business lease on an EV instead of on an ICE car is a no-brainer, thanks to government incentives.
And, a business lease is for a set period, so it's not very likely that people will get their cars changed more frequently at result of these incentives, instead they'll simply get an EV when the lease is next up for renewal.
Will they get nicer (I.e. more expensive) cars than they did before, now that the BIK on EVs is low? Possibly, though with the low BIK the net cost to them will still be the same.
So for these group of users, an EV makes perfect financial sense.
But for anyone not getting their EV on a business lease, the financial benefits are less obvious.
And, as you rightly pointed-out, they might change their cars sooner than they normally would, in order to get an EV, which of course means more expense for them.
However, there are many reasons why private owners buy EVs.
Firstly, perceived savings is a very common factor. Private owners bought Diesel cars for years "because they are more frugal", Londoners bought Prious because "there's no Congestion Charge", etc - many private owners look only at very basic data such as fuel economy or insurance group, and are rarely bothered with TCO that takes into account depreciation, maintenance and servicing costs, etc. For these owners, the allure of 4 miles per kW at 12p per kW will be a significant factor, ignoring all others.
Then, many will buy an EV for a range of non-financial reasons. Because it's 'the right thing to do' (the government says so), or because they feel (rightly or wrongly) that they are 'doing their bit for the environment', or because they only do short local journeys which fit well with an EV, or because they are technophiles, or because they want a car that does two-point-something zero-to-sixty, or because they want a fun car, or because they want the neighbours to be envious... the list is long. To sum it up... there's zero financial benefit in buying a C63...
and yet I always wanted one (too late for me though....).