The language here tends to get in the way a bit.
Generally “reaction wheels” are used for pointing: you turn them, then stop turning them once the satellite is pointing as desired. They’re not meant to spin rapidly to soak up a bunch of angular momentum. If you just need to control pointing, a reaction wheel system isn’t going to be able to absorb the angular momentum of high rotation-rate tumbling.
“Momentum wheels” are generally built more massively and capable of higher rates so that they can soak up significant angular momentum. But they’re not common in small satellites (because they’re generally not small)
“Control moment gyroscopes” are the ultimate form, but are only seen on larger craft.
I think the general answer is that building a system to internalize the initial tumbling’s angular momentum just isn’t worth it: there’s no other need for that hardware, and you need the magnetorquers to offload angular momentum anyway, so use those.