Wherever something passes through the roof—pipes, vent stacks, cables—there’s a potential leak point. Sealant around these penetrations can crack, shrink or detach over time due to sun, temperature changes and movement.
A quick look to see if the sealant is still flexible, fully attached and not peeling helps you catch small failures. Re-sealing a small ring around one pipe is easy and cheap; repairing a big leak inside an apartment below is not.
It’s like checking the frames around windows—you focus on edges, because that’s where water loves to sneak in.