Because otherwise, people would be able to use non-Tesla GPUs for cloud compute workloads, drastically reducing the cost of cloud GPU compute, and it would also enable the use of non-Tesla GPUs as local GPGPU clusters - additionally reducing workstation GPU sales due to more efficient resource use.

GPUs are a duopoly due to intellectual property laws and high costs of entry (the only companies I know of that are willing to compute are Chinese and only a result of sanctions), so for NVidia this just allows for more profit.