Lithium batteries still have limitations with charging at low temperatures. OEMs can design systems that will warm the battery up to a temperature where it can be charged after the car is started, but it’s not nearly as simple as dropping a lead-acid battery in.
Integrate the new-fangled battery (of whatever specific chemistry), the BMS, and the heater into a box with just two posts on top (just like lead acid batteries have had for over a century). It can be designed to take care of itself.
And if it's cheap enough to produce and sell, and offers good enough performance over its normal usable lifespan, then it doesn't need a diagnostic interface for sorting out issues any more than a lead acid car battery does today.
