As others have said to some degree, the sensors on a jumpship are much more powerful and longer ranged than those on an aerospace fighter.
Having fighters around to provide an active defense in case of a threat, that's one thing. Using fighters as some kind of system patrol/early warning system is not very effective. Satellites and jumpships, and space stations and even some system patrol/defense dropships can do the job extremely well. What you need/want is long range sensors and the operational endurance to keep monitoring 24/7 for days, weeks, months and even years. Aerospace fighters are too valuable in combat to be tasked to patrol someplace quiet.
Aerospace fighters are for combat, or sneaky recon stuff in hostile territory. When you consider the actual size of space and solar systems and jump points even, you realize that aerospace fighters are teeny tiny with limited sensor capabilities compared to everything else.
That's not to say aerospace fighters never fly CAP, but I feel like you'd need a specific reason, like an elevated risk of a threat because you are in the middle of a combat operation, or maybe just a desire to give your pilots some cockpit time and have them fly a nav point circuit. What happened with Taskforce Serpent's CAP could fall into either category, or both.