IN a foundation set, those sorts of 'tricks' are often the best way for students to do basic percentages. 25% - divide by 4, 50%, divide by 2, 10%, divide by 10, (possibliy 1%, divide by 100), and then from those, make whatever percent you need. Often the questions only use 25% or 50%, especially on a non-calculator paper.
If you teach them divide by 100, many of them would struggle with that, because they might try to use bus stop method or some longer calculation like that because they aren't confident with place value. If they do divide by 100, and are then faced with a decimal, they don't necessarily know how to multiply with decimals. And then if they do know how to multiply, they might get confused with using a 2-digit number like 25. Much easier to do something like 36 divided by 4 than for them to try to do 3.6 x 25.
yes it would be great if they understood that 25% is the same as 1/4, and that finding 1/4 is the same as dividing by 4, and chances are that they've been shown that many many times ,but if they're struggling with maths and are at a resit level, chances are that it hasn't really gone in or made sense. If I had lots of time to go back to the beginning and start over with some pupils with basic fractions etc, that would help - but often they are much more interested in merely passing the exam, and don't really care about the 'why' of it. They know that there are non-calculator ways (the shortcuts) and calculator ways that may be faster, but many of them prefer the shortcuts along with 1%.
But that said, I'd be happy if someone wanted to use another method that they had remember and were correctly using, if they could do it fast enough and without a calculator. I might point out that there are faster methods (like dividing by 4), but they'd certainly get all the marks for doing it a longer-winded way.