To counterweight all the cynical takes about soldering RAM being a conspiracy to force device obsolescence, I can think of at least one other dynamic that could have resulted in today's scenario: smartphones.

Smartphones also need RAM and are especially subject to requirements of always being thinner, lighter, and have a durable battery, yet have spacious amounts of RAM.

Growing demand for smartphone RAM pushed for its optimization and production scaling and since all its requirements also match laptops, this convergence was inevitable.

Hopefully the growing demand for datacenter RAM density will make modular interface standards like LPCAMM2 more available (soldered has no place in datacenter).