They've also redesigned the HEAT round to do well from the smoothbore tubes. Spinning a shaped charge is not ideal.
The British (and clients) were the main holdouts for going smooth on tank barrels, as they liked and had plenty of HESH (high explosive squash head, a round that transfers quite a slap to thick armor), but even the Challenger II had an upgrade programme* replacing the rifled tube with a smoothbore. So to Dr I day that rather than being the exception on modern tanks, the smoothbore main gun tube is now the rule. cn
*had it been an Abrams, "program"