Where I work we need to submit proof of insurance to drive our own vehicles to job locations/for work purposes, but we are still covered under an employer polic

Where I work we need to submit proof of insurance to drive our own vehicles to job locations/for work purposes, but we are still covered under an employer policy when driving for said business purposes. They just don't want to deal with drivers whose vehicles aren't already personally insured (which seems sane). My understanding is that this is pretty normal, though I'm not 100% sure if it's an outgrowth of liability concerns or legal obligation. Either way, I can't imagine that Walmart wouldn't have a similar practice in place. Not that I disagree that Walmart's cutting out hypothetical fleet maintenance costs with what they're doing. I'm sure there are a variety of advantages for them however they're structuring it.