Micro guides are nothing new. They've been around for ever on ultralight rods as well as some technique specific setups used in Europe and Asia. In the last 15 years or so, rods (bass rods more specifically) have undergone a marketing shift towards being as light as possible.
It used to be that you had to keep paying more and more $$$ to shave off each gram of weight - using higher modulus graphite, titaninium guides etc... well - micros get you that weight savings and they 1/10th price of a set of titanium guides.
As for why you don't see "veterans" embracing this, well - i've seen plenty of respected builders using them as well as read multiple articles about the pros/cons written by them. I think any of them will tell you that in any situation, use the smallest possible guide that will effectively and efficiently do the applicable task. In cases for bass fishing, in nearly every situation - a size 6 (standard single foot size) is more than sufficient, so why not a 3 or 4?
I think its not so much the builders are not embracing them, but the buyers of custom rods might have some trepidations about spending big bucks on something that is not the industry norm - cuz lets be honest - if you came to me and said "I want X, Y and Z so its as light as possible" and i told you "X, Y, Z will cost you 350 bucks... i can do "A, B, C" and make it lighter for 200 though."
You'd probably be skeptical.
