Years ago I would have been doing exactly the same, Tigger, when I was fishing waters I'd fished for years, knew every bump on the bottom, and what fish/size were in the water. Unfortunately in my absence from the coarse scene, rivers have changed as have the species/populations, lakes too.
When you know what you're likely to get in a swim you can fish with less doubt and not have to hedge bets, chop & change, make much in the way of terminal rig adjustments. Even fishing local commercials for Roach, Cru's and Tench you can attract attention from voracious mobs of large-ish Carp which can wreak havoc on 2-3lb Maxima fished straight-through! So one uses say 6lb reel line with a 2lb bottom - IF you get bust-up by a double then you've minimised loss of tackle and stress to fish (?) - on the other hand you've still got a fair go at catching your target fish!
A very similar situation occurs on rivers whilst roach, dace, chublet fishing when you can be given a similar beating-up by barbel or even spotties! Even on former no-hope rivers like the Irwell and tributaries where there have recently been reports of barbel showing - as well as brownie doubles! You just don't know what you're likely to catch on some waters anymore!
Until I explore these waters a bit more I don't feel confident in fishing reel-line straight through!
Tight Lines!