Blades have the basic issue of "how often do you want an unpopulated chassis?" - answer, never.
So really they're solving for replacing a failed piece of hardware.
But how often do you need to do that, what's it worth to you? If it makes sense then the statistical window where it does is tiny.
And if you own more then 1, like an entire rack, then do you even care? Because above some scale you're just going to wheel the rack out rather then go and pull individual units.
Basically the scaling is against you: for a highly manageable bladey rack unit, you've got to be small enough that one server matters, large enough you need the swap out to be low labor, but not so large you could just wait for the rack to go down. And this has to be worth enough to justify the price premium and vendor lock in (because at rack scale you just buy a rack of the cheapest whatever from any vendor and make them compete on price - at one job bringing our computer management in house triggered an immediate 10% price drop because we threatened HP with using another supplier at all).