What's in it for the contractor to offer to take cash payment and not charge taxes? If they charge the taxes, they pay them with our money anyway. If they write off the taxes because we pay cash, they don't pay the taxes, which they wouldn't in both cases anyway.
The only advantage I can see for them is that if they offered a service for something optional that the client wouldn't do because it's too expensive, asking for cash payment to avoid charging the taxes might make said service more affordable, which allows them to make more than nothing since the client would have otherwise turned down the offer.
Also, legally speaking, I feel it gives them an open door to cut corners to increase their profit margin since you couldn't sue them because it would be like calling the cops for someone stealing your marijuana.
The only advantage I can see for them is that if they offered a service for something optional that the client wouldn't do because it's too expensive, asking for cash payment to avoid charging the taxes might make said service more affordable, which allows them to make more than nothing since the client would have otherwise turned down the offer.
Also, legally speaking, I feel it gives them an open door to cut corners to increase their profit margin since you couldn't sue them because it would be like calling the cops for someone stealing your marijuana.