The use of deep groove ball bearings in bicycle wheels is a flawed application for them. These bearings, sometimes erroneously called sealed bearings, are not intended for applications with any sort of side load at all. Unfortunately cycling gives them plenty of side load.
The second problem with them is that they require perfectly machined seats. They don't get that in bicycle wheels. Any high or low spots or out-of-spec spots in their circumferential compression when they are pressed into their seats will add to quick destruction. The steel races appear to be indestructible to the layman but they are actually quite sensitive to poor seats. Bicycle hub seats are terrible. They're not round, they're not within spec and they are distorted by spoke tension on the hub flange.
The third problem is that sealed cartridges are not intended for water contact. A single seal cannot separate two fluids - water and grease. The rubber seals have to be protected by an additional non-contact seal such as a labyrinth seal. This seal has to designed correctly. On bicycle hubs these are sometimes called dust caps. Most are just flat discs but they have to be C-shaped and turn inside another C-shaped part in the hub. To envisage how they are supposed to look, make a C with each of your hands. Now bring the two Cs together and offset them and let them nestle without touching. Now imagine them rotating around each other. That's what the outboard seal on a hub should look like. You'll see that if water splashes on the C, it will drain out the bottom without entering the hub. These seals are not submersible and can be ingressed by strong spray such as pressure washes, riding in the rain with the bike on a roofrack, etc.
The fourth problem with sealed cartridge deep groove bearing is axle distortion. If the axle distorts, such as on a rear wheel wheel when pedaling, the bearing distorts in its track and it is compromised.
The fifth problem is that people buy wheels based on weight. The lightest wheel is the best, according to the "reviews". Light wheels mean small, undersize bearings (American Classic is a classic here) that just cannot handle the load. Boutique wheels just about all use cartridge bearings because it makes manufacturing cheaper, the bearings need no design, they're just chosen off the shelf according to size and are simple to fit.
The sixth problem but the least of your problems, is cheap or expensive rubbish bearings. Some are really rubbish. Ceramic bearings are a very bad idea and they cost a lot of money. People flock to stuff called ceramic but have no clue what they're getting themselves into.
All these problems (apart from poor sealing) can be overcome with the use of angular contact bearings such as used by Shimano and Campagnolo. Unfortunately these are expensive, proprietary and requires large manufacturing runs. They are also unpopular because they are not considered as "Sealed bearings". This is erroneous because they can be sealed and they are in fact, sealed very well, especially those from Campag and Shimano which have contact seals and labyrinth seals of the right design.