Because the enterprise disks are rated for years of continuous service and have things like firmware which doesn’t lie about whether data has been committed durably for the sake of benchmarks on review sites.

None of this means that you should trust any particular disk enough not to need redundancy, backups, etc. Companies can and do make trade offs based on their needs and management competency and people have been shifting software for a generation to rely less on the hardware – back when Sun announced ZFS, one of the major appeals was that you could drop expensive hardware RAID controller dependencies in favor of cheap boxes of disks – but there isn’t a single global optimum point. A lot of enterprise purchases are driven by being able to satisfy your most demanding users with the same service as everyone else so you can avoid needing your admins to be trained and experienced with dozens of different storage systems. That last part especially extends to testing: for example, does your rack of consumer drives with software redundancy come back up cleanly after a kernel panic or power outage, especially a nasty one like a fluctuating brownout? Depending on your budget, needs, and technical bench depth you might reasonably conclude that the savings are worth the ops work, or that it’s safer to pay an enterprise storage vendor who’ll certify that they’ve done that testing and will have tech support on-sight within an hour, or that you’ll use AWS/Azure/GCP because they do even more of that tedious but important work. All of those can be right, but I’ve typically found that people in the first two categories think they’re doing better than they are and would be paying less for better service in the cloud.