"It's only a small leak, it can wait"
Leaks rarely stay small. Left long enough, even a minor leak eventually causes timber and insulation damage that costs far more than an early repair would have.
"The leak is directly above where I see the damage"
Water travels along timber before showing up inside, often well away from the actual entry point. Chasing the visible stain rather than tracing the source rarely fixes anything.
"Sealant is a permanent fix"
Sealant applied over a leak is a temporary measure at best. It doesn't address whatever caused the original failure, and tends to fail again within a season or two.
"If it's not leaking right now, it's fine"
Some leaks are intermittent, only showing up in certain wind directions or rainfall intensities. A dry day doesn't mean the underlying fault has gone away.
If you're dealing with a leak, however small it seems, a proper survey is worth more than guesswork.