Using SSD is kinda "throw more hardware at the problem so that we don't need to fix our precious crappy software" type of solution.
Especially when it indeed is "crappy software" that will take major effort to rewrite/refactor.
Hardware is cheaper than developers, and the former doesn't fail to deliver half as often as the latter...
Also, you need to compare the cost of a single developer who fixes innodb to the cost of hardware incurred by _all_ users of innodb who would benefit from the solution.
Trying to fit high I/O workloads on spinning disks is a lot like spending your efforts to make your program run on 64K RAM. An interesting challenge, that would surely exercise your coding skills, but would not deliver the optimal performance.
It is hard to see the benefit of ignoring SSD to get high I/O performance vs. redesigning the software around I/O bottlenecks.
Redesigning software to work on bad hardware is definitely a challenging project, but not always the best use of resources.