A combo probably isn’t going to be the ideal option for a more experienced angler who already has a lot of gear. As the combos are usually specific in matching the reel type with a specific rod, they might find that either component is incompatible with existing tackle that they plan on using.
For those with more money to spend and willing to invest in their sporting equipment, a combo can also be something of a hindrance. Having a go-to baitcasting rod that someone has already had a ton of success with is vastly improved with a new high-end baitcasting reel of their own choice.