Because when it comes to real practical advice on specialist experimental techniques I may as well be talking to myself. It seems to be singularly useless.
It's always amusing when (insert branch of physics here) complains about how few (insert branch of physics here) experts there are and we're just overrun with (insert opposite branch of physics here) questions/people. The theoretical folks complain(ed) all the time there was too much applied physics and not enough theory. The people who want homework help complain there is too much advanced physics. Experimentalists complain there's too much theoretical physics. Maybe if I get motivated, I'll go through meta in the past 2 years and pull together all the various times this comes up.
Anyway, I'll address the idea you are raising rather than the (albeit mild-mannered) rant in the text.
Yes, there are disappointingly few experimental physicists on the site. And many experimental questions go unanswered or get threatened with close reasons as being too engineering, or not about physics, or whatever by people who don't conduct experiments.
It's unfortunate for sure, but we want experimental physics questions just as much as other areas. We simply don't have the people here yet in a critical mass to make it work well. We have the tags for it, we have a few people excited to answer questions about it, but it also has to be questions about experiments we can answer. I would love to answer questions about experiments in fluids (analyzing results, measurement techniques, etc) but I would be completely useless to answer particle physics experiment questions.
So there are two things that people who want to discuss experimental work should do. First, get other people who conduct experiments involved. If you are actually conducting experiments, odds are good that you have colleagues you share lab space/equipment with. Get them on the site too so that way we start building an experimental sub-community.
In the mean time, the second thing you can do is be proactive in defending your question and make sure you include the experimental-physics on it. Don't say:
"What kind of filter should I use to record XXXnm wavelengths?"
and leave it at that. Because to many people, that would be off topic (and to the rest of us, a poor question). Instead, say:
"I am designing an experiment to measure Y under conditions X. I know it radiates at A, B, C frequencies and I want to capture phenomenon D which occurs primarily at wavelength XXXnm. How do I set up my camera to record this?"
because then it clearly communicates that you're looking for an answer to a physics experiment and not just trying to come up with some new app that's a Instagram-Clash of Clans-selfie stick integration tool (this post hereby counts as me establishing priority for copyright on such a tool!).
It opens up some good avenues of discussion because experts can give advice on the experiment overall -- maybe there's better ways to set it up or other things to consider (like maybe all the glass in the world happens to filter that particular wavelength and you need to do something special). And experimentalists who are researching how to conduct similar work can find the answer here and say "Wow, a place to ask/answer experimental questions? Awesome!"
Having an awesome repository of questions and answers is what draws theoretical (and for better or worse, homework) questions and experts, so let's build up the same repository for experimental ones.