Cloud saves are for playing on more than one box as well as backup. Achievements, from the developer’s POV, give some insight into player behaviour, you can also drop hints there (I would never have tried to pet the manta in Satisfactory otherwise), make suggestions for tasks people can set themselves, etc. Whether you, as a player, cares honestly nobody but you gives a fuck.

I can tell you, for example, just from the achievement statistics, that a metric fuckton, an absolute majority, of Cities:Skylines players play modded. They do track city building milestones and very very few people are reaching anything even close to mid-game with achievements still enabled.