"Fixed that for ya' ..."
To
other people, it's sometimes a fundamental and essential part of the way they make their livings through their trading, because their results have proven that it collectively maximises their edge.
It can be a way of combining locking in some profit on a trade with also taking the opportunity to develop further profit.
People vary greatly in the relative extents to which "fear of losses" and "fear of missing out on potential profits" affect their decision-making.
Personally, with
some of my entry-types (the ones for which I've reliably proven it to be beneficial, naturally enough), I close a proportion of the trade at a level which locks in some collective profit
on the whole trade, and let the rest run (if it will) adjusting its stop-loss manually as it does so. (That applies to
some of the trades I make which
might catch the start of a new intraday trend, following a reversal.)
Van Tharp, in his book
Trade Your Way to Financial Freedom, shares your view that scaling out is, broadly speaking, a bad idea, because it tends, overall, to lead to having most at risk at the times when the odds tend to be least in your favour, but there are definitely some exceptions to that (including some of the methods I routinely use, myself).
So, these things are a little more complicated than one expects from the superficial view, and the reality is that a whole range of interacting variables can sometimes be involved,
even occasionally in ways that change the validity of the conclusion.
One size does
not fit all.
