Originally Posted by
Kapusta
Bearing type has nothing to do with TA vs QR. For example, all shimano hubs are cup and cone, their TA hubs are no different. In fact, For pretty much any hub model offered in TA and QR, the bearing type is going to be the same between them.
What you have seen (TA being all sealed cartridge bearing) is probably due to the fact that higher end and/or newer hubs are more likely to be sealed cartridge bearings (Shimano being one exception), and the same is true of TA frames and bikes (higher end and/or newer). It's a correlation thing. Higher end/newer frames and forks tend to have higher end/newer hubs on them.
Cartridge bearings are much more common with through axles because through axles tend to be higher end items.
Looking at Shimano's bearings, I can also see that engineering a cup and cone through axle is far more difficult than engineering one for cartridge bearings. Frankly, it looks like Shimano should have followed others lead as the cost of replacing a through axle cup and cone system when it inevitably wears out is going to be prohibitively expensive.