This is a space saving device in a way, and a standard notation for a multistep calculation (i.e. not an equation). It is roughly like the following calculation
Are you really suggesting that such a calculation should be split into multiple lines simply so that there would be a single equal-sign on each line? Admittedly that is
sometimes an improvement - largely for reasons of lay out. But that wastes quite a bit of space. For example, the above calculation could then look like
Mind you, I do split a calculation on several lines, if the intermediate steps don't fit into a single line.
On this site saving space is not a major concern. But it becomes so, if you want to fit the calculation on a single slide. Or if you need to squeeze a set of homework problems on a single sheet of paper.
If we did the same in the linked question it would look like
It may be quicker to read. Easier? I don't think so. But it also consumes a lot of space, not to mention keystrokes of TeX-code:-)
The upshot is that this is such a trivial calculation that giving it this much space just feels wrong. Due to its relative unimportance.