[planb]

The tricky race conditions are the ones you often don't see in the debugger, because stopping one thread makes the behavior deterministic. But that aside, for webapps I feel it's way easier to just set a breakpoint and stop to see a var's value instead of adding a print statement for it (just to find out that you also need to see the value of another var). So given you just always start in debugging mode, there's no downside if you have a good IDE.

[pjmlp]

Using a debugger isn't a synonymous with single stepping.

[spongebobstoes]

Even just the debugger overhead can be enough to change the behavior of a subtle race condition