Generally speaking, it's probably for both reasons. The longer the pole, the more severe the bend in the tip will be when lifting/swinging the fish over the side. That's usually a broken tip waiting to happen.
When they're thumpin your jig, you're probably gonna stick them pretty good (and probably deep in the mouth) ... so those times you might worry less about "losing" a fish, bringing them in --- but, when they're biting much lighter, or short striking, and you still stick them, they have a tendancy to be hooked in the lips or not hooked very good, and that's when getting a net under them will save most of them from getting off.
The weight of the fish vs the line test (& condition of it) is also a possible concern. I've seen partners of mine fight a good sized fish to the side of the boat, grab the line & start to lift the fish over the side ... only to hear the 4lb test line snap. I'm using the same line, catching the same size fish, and hand lifting them over the side, without breaking the line & losing the fish. The only difference was "HOW" the lift was done. Their lift was more of a hurried "I'm gonna lose him if I don't get him in quick" ... where mine was a more experienced slow/steady lift, not creating more "weight/pressure" against the line than what the line can handle. These were only ~2lb fish, but a quick lift against that weight was enough to add more than 2 more pounds of pressure (weight) against the line.
Nowadays I carry a net onboard ... but, since I don't use rods over 9' long, it's not one of the long handled ones.
... cp