Once again, the poor subsidising the pleasures of the rich it seems
Generally, a subsidy like this is to get market exposure for something so that the price comes down to an affordable range.
In the last 10 or 12 years, the price of battery capacity has declined by about 85-90% (i remember when the first teslas came out here in the states, the financial disclosure from tesla put the cost of the battery above the selling price of the car). The battery in an extended model 3 is probably about $10k US now.
I'm not normally a fan of the government incentivizing high cost items (they usually just stay high cost), but this appears to be a case where it's paid off in battery technology - the volume is there now. There's also not much incentive in the US for tesla's 3 now, at least at the federal level, and gas is CHEAP here, about $2.25 a gallon, but the 3s are still selling hand over fist and attracting more players.
There's not a clear reason not to incentivize here (we had fits of stupidity about 10 years ago with the government deciding to subsidize solar panel making, as if you'd convince buyers to pay significantly more for panels when China had gotten past us in terms of technical advances. That was a prior administration's viewpoint, though. We'll just throw money at it and it'll somehow get better. I guess making a reliable car overseas is a taller order than making superior solar panels (when the cost/benefit for panels is so clear cut, i'm not sure why we wouldn't want to use the least expensive panels we could find, anyway).
I ride public trans, and use a gas car - no dog in the fight. I don't mind subsidizing tesla's cars as we certainly subsidized oil and continue to do it, and we do something many times dumber here - we use half of the corn crop to make motor fuel and then subsidize farmers to grow it (when we don't otherwise need it). and then give them preferential treatment on appreciated land value as if it's somehow not worth real money.