E+C is not for everybody, it doesn't scale on very large programs that use a lot of static libraries. They'll prefer retaining the ability to edit code while the program is running. E+C only allows editing with a breakpoint active and insists on being able to compile changes to continue running.
Sure, it has an effect on perf. Indirectly because it requires a debug build with the optimizer turned off. Directly because of those stack reservations, you'll hit this site's name a lot quicker. Working with smaller data sets to debug the program is typically pragmatic or necessary.