I think the main problem is that the majority of wheels are now 19" to 20" in design, which means that even if the spokes were similar in size, near the hub, they would have to be super thin by the time they tapered down and reached the barrel.
IMO - one of the best 5-spoke wheels are the Forgestar CF5 in 20"
I don't think that size is really the issue, I think there is just a lack of market at the moment. Someone else let me know that there is now a 19" tarmac wheel, but only 9.5" width unless going custom 3-piece.
The forgestars are one I've seen and just don't quite fit the aesthetic I have in my head. I'm thinking there has to be a wheel out there, just haven't seen/heard of it yet. CCW lm5 is close, but only comes in 18"...