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We called it the "check"I've never had a reel without a switchable 'backwind' but can't see it would be a problem.
I'm terrible if out fishing & yapping (!) for sometimes winding in a little too much before another cast, so it is handy to be able to switch the backwind off for a second to let some line back out rather than fiddle with the drag.
Only if you use the backwind to play fish. Not a lot of people do anymoredo spinning reels with no backwind cause problems.
Personally I like my drag set very tight and rely on backwinding as I feel more in control. It's not as if bass run fast and a loose drag just causes problems if a decent pollack or wrasse takes the lure. Conversley you can backwind like buggery if a sewin takes the lure to get it's head downIf using braid no, as above just get used to using drag. If using mono just using drag can put un wanted coils in your line.