Because they can and their customers will continue to purchase new models...
But...over on the commercial/industrial side...they keep their revisions
backwardly compatible as much as possible...because those customers typically
will NOT purchase again...or delay purchase until there is a significant
benefit
Mainly because commercial/industrial keep their equipment for decades or
longer. So spare parts and replacement part interchangeability a critical
decision point
The philosophy of Corporate parts bin and compatibility is getting lost
with the new designers & their management.
They even used to include the pig-tail harness. but no more
The whole vehicle harness still (that I know of) has the tow/trailer
wires 'n there' and am expecting the OEMs to remove that as a cost
savings thing all too soon...as the percentage towing is very, very
small...and...the OEMs can then make money from those who then purchase
the tow harness(s)
Can also see the 7 pin connector change with more connections. That
will be when there is a complimentary computer/sensors/etc on the
trailer. Mainly a strain gauge for the computer to know if over loaded
or not...