A lot of good points on both sides of the coin here.
OP, I agree with you overall. My experiences are purely anecdotal, but I find that spinning plates is a lot of fun for about 6-7 months in any given time and I begin to feel sort of numb to it. Casual sex is easy but it gets monotonous and the “rush” of banging a new woman loses its excitement for me fairly quickly. On the other hand, I think the overall positive feeling from an LTR that is going well outweighs spinning plates.
The problem of course - as others have already pointed out - is that that positive vibe from an LTR is also temporary. Add into that that the fallout from LTR can set you back emotionally in far greater a magnitude than a plate and I can see how it becomes a toss up. So far, it seems to be when, not if, a LTR goes bad. I hope to be proven wrong by this someday.
Bottom line: I agree with you: but also see why many DJs would simply prefer to spin plates.