You are correct in that FRT has been used in recent years, as a disincentive, to slow the increase of private car ownership. However, as EVs have been exempted for approximately 20 years now, the FRT also clearly has an environmental component. Even hybrids used to get FRT tax breaks (until very recently). In most other countries, EV tax breaks have been used to offset the increased cost of the EV batteries, when compared to ICE vehicles. To make the cost of buying an EV comparable to that of an ICE.