One problem is that without broad adoption, support even in niche cases is precarious; the ecosystem is smaller. That makes the codec not safe for archiving, only for distribution.
The strongest use case I see for this is streaming video, where the demand for compression is highest.
Could you explain what you mean by "not safe for archiving"? The standard is published and there are multiple implementations, some of which are open-source. There is no danger of it being a proprietary format with no publicly available specification.
As a counter, J2K has been well established by the professional market even if your mom doesn't know anything about what it is. It has been standardized by the ISO, so it's not something that will be forgotten about. It's a good tool for the right job. It's also true that not all jobs will be the right ones for that tool
Truly standard ANSI C along with a number of other implementation strategies (LLVM IR seems unlikely to be going anywhere) seem just as durable as WASM if not more, but there are applications where you might not want to need a C toolchain and WASM can be a fit there.
One example is IIUC some of the blockchain folks use WASM to do simultaneous rollout of iterations to consensus logic in distributed systems: everyone has to upgrade at the same time to stay part of the network.
