What's to stop the Classic team from implementing segwit? AFAIK the coding is mostly complete, and publicly available.
The Classic team depends on their brainwashed superstitious cargo cult for support.
That cult's totem and taboo structure worships larger blocks and despises any innovation supported by Core.
Classic won't even allow its users the option to enable RBF ("Because Controversial").
They only accepted CLTV because somebody called it OP_HODL and the anti-Todd lynch mob subsequently threatened to turn against them, for withholding a suddenly popular feature.
There's no way the Gavinistas will admit segwit is a good idea, precisely because it was proposed by Evil Blockstream People.
The other side thinks SegWit is a gross kludge of code. If they just copy it, what was the point of all this? What was the point?!?
quod erat demonstrandum