First, I believe it was a labor of love (for ST) on Brad’s part. I think this was the case for most/many of the early reproduction prop producers (Wegmann/Heilman, Deschennes, Miarecki). There is a purity to that motivation that really appeals to me as Star Trek fan.
Second, I think that Nelson phasers are really works of art. Not only is the design aesthetic visually appealing, but he went ahead and added the electronics that are so cool (which for the time was unheard of).
And lastly, there is the tie-in the Phase II and Gene Roddenberry…