They do, your just not asking the right questions.
Actually, thinking about it, Engcon might not do one now (in this country at least) But Rototilt and I see above from
@APhillips, Steelwrist, certainly do.
On the subject of control systems, they are expensive, especially on the smaller machines pro rata. But dual aux's cost money too, which goes some way to reducing that cost. And there are some advantages, even on the smallest machines, to having one. Which for some people wont be worth the cost, but for others, it will.
There is no right or wrong tiltrotator build - whatever suits your budget and work is right for you.
I realise I'm starting to sound like LGPEddie did 10 years ago... I didn't have one back then. And now I do, I sort of understand where he was coming from.
Interesting that the conversation hasn't really moved on much with the humble tiltrotator though. And most innovation I see with them is to do with making them easier to install rather than more functionality. Although mic4 and openS are interesting standards that would make life a lot easier for us all.
But those of you without control systems wouldn't be interested in that