I also noticed this little trait a while back

I have my own ideas as to why they pull. If you're getting a good heel off lead or more importantly when you drop the lead you may be able to use this to your advantage. I used a long lead, a couple of yards long and a harness. You start her off walking to heel with the lead held short and if the lead starts to go taught stop, release the full length of lead and walk the other way. You may also find that if the lead held short goes taught sometimes just dropping the slack (whilst holding the handle) may stop the pulling. Also as has already been mentioned, when Meg is trying to break the heel position if you walk into her path gently putting your knee in her way and then progressing in "your" chosen direction and then moving into another direction this also seems to work. Basically remember that it is you taking her for a walk not t'other way round.....keep her guessing where you're going..... start in familiar surroundings with few distractions and help her build the habit of walking by your side. Most of all don't loose heart or your temper for that matter

You should get there eventually
I have been there and even to this day we have to do occasional reminders of who is walking who but we are progressing nicely. What gets my lot pulling and forgetting their manners is new surroundings

so we're about proving the heel walking at the moment. We've just got back from Cropton...great forests, loads of rabbits and grouse and phessies

the bloomin things even walk yards away from the caravan all over the camp site....now just imagine me managing 3 springers on their morning walk........you may laugh
One other thing to try.....when Meg stops at the end of the long taught lead, call her back to your side..."Here" or "Back".....mine have all learnt this well and will stop their pull and about turn and wait by my side.
I've never tried Canny collars and the like but started with a semi choke collar adjusted to just tighten not choke (good to start for walks of low distraction) then harness (where lots of pulling is likely) and useful for holding a dog on a peg and now our regular walks and forays into the woods etc. a slip lead is all that is required.
Sorry to be a bit long winded, hope this helps
Steve