Umh, here are a few reasons why some providers don't verify...
1. The provider contacts them asking about Joe Blow but doesnt provide his name, number, handle etc.
2. Provider contacts you without verifying who SHE is, just asks if Joe Blow is LE lol (providers dont randomly give out clients info, so if we cant verify the provider we wont bother replying)
3. Providers travel and often aren't able to check their mail as often as possible
Other reasons could be the provider thinks they are going to lose business so wont respond
Which I think is dumb, if the client only has you and another provider as a ref. he's going to find out sooner than later that you didnt verify him and not see you again.
And some providers are simply lazy lol and just dont respond.