Changing character models (something I've always wondered about)

Question for developers who’ve worked on big AAA games: why do models representing the same character change noticeably, to the point that they don’t look like the same person anymore?

Some recent examples:

Faith in the Mirror’s Edge games (face is a lot fuller in the more recent game)–in both games we only see her in cut scenes. Actually, bad example, the ones in the earlier game are very stylized.

Talion in Shadow of War vs. Shadow of Mordor. In SoM he looks a LOT like Aidan Turner (Kili in the Hobbit Movies, the new Ross Poldark) and in SoW he just looks different enough to be a different person.

Lara Croft’s face seems to change in every game, even across ones that are meant to be tied together (say Tomb Raider 2013 and Rise of the Tomb Raider).

I understand if it’s been so long between games that the digital assets are lost or something, but otherwise I’m kind of mystified, particularly when it’s only been 3 or 4 years between “versions” of the character. Why don’t they just keep using the same model, or really work to make the newer one recognizably the same person? For instance, in what I’ve seen of Wolfenstein II: The New Colossus, BJ looks pretty much like the same guy as the guy in The New Order.

Maybe because the tools used for the characters evolve? Lara Croft essentially grew better as the technology grew better?

Because then people would accuse the devs of being cheap for reusing the models?? I wish I was kidding, but specially in AAA there’s a tendency to do everything again to justify costs.

Take as an example Destiny 2. The assets of the first game are good enough and in most places a re-entering would have brought them up to par with most contemporary games, but since it’s AAA and it needs to look the best they can they redid most assets from start (keeping them recognizable, though). They could instead have reused a lot of assets and instead put the effort on new, additional enemies to double the scope of the first game, but again, the optics of that to the client in the current climate are hard to manage.

If you look at more budget conscious products you will see far more reuse of previous assets that still hold up, or plain texture revisions, etc…