I don't understand why some people always like to keep their MA discussion "pure within their own style".
Depends on the discussion, and the martial art. Having a clearer understanding of that, and not thinking that all martial arts are the same, or have the same goals, reasons, aims, or anything else, is the first step to actually getting your answer.
Most of the time, the guy you have to fight in the street will not be a guy from your same system.
Who says that all martial arts are aiming to deal with "the guy in the street"? And who says, even if you do end up wanting to apply it against such a "street guy", that he's even trained in anything at all? Realistically, if your aim is to train against the "guy in the street", you don't need to look to other martial arts, you need to look to the realities of street violence… how it's set up, how it happens, common attacks, and so on. You're not going to go up against another martial artist.
You will need to know how people in other styles may think and train in order to be able to deal with them effectively.
Unless you're going into a multi-style tournament, you're not going to have any reason/need to know how other arts do things. You just don't. It's wasted effort.
I'll be more interest to know how a MT guy uses his double neck tie than a wrestler does. The reason is simple. I know how a wrestler will do, but I don't know how a MT guy will do. To be able to deal with a MT guy's knee during clinch is extreme interest to me.
You might want to understand it just because, well, it's always interesting to have a wider understanding, but looking to learn how each system does all their variations of whatever you're looking at, well… it's unrealistic, impossible (from a practical standpoint), wasted effort, and largely pointless. Additionally, it's assuming the same thing you always assume… that what you find in one art is also found in all others. I've lost track of the number of times you've come into a discussion of how a particular martial art does something (specifically in their form) to give very general ideas of something you think is similar, which is almost always out of place in the discussion you're joining in. It happens here, on MAP, everywhere. And, honestly, the blowback from that, I believe, is really where this thread has come from.
Waste of time and effort the way it's shown here.
When it comes to discussions, well… it really depends on the discussion.