garden drainage issues

[Nearlyman]

I have read with keen interest the posts re garden drainage issues. It occurs to me that, if the advice offered by contributors is unanimous in its recommendations that a [commonly very expensive] 'land drain' be installed, how is it this very undesirable and no doubt worrying characteristic of the plot - which must have been, at some stage, a building site and patently obvious to the builder/developer - wasn't "flagged up" by the builders'/developers' geographical survey or otherwise been known about by the local government Planning Department, and on record for inspection by the purchaser's lawyer during the conveyancing process?
Remember, every house sale now requires a Home Report Document Pack: if you were not told of this undesirable characteristic of your property do you now become liable (by default) to reveal it in the your Home Report Pack for any prospective/future buyer?
In hindsight I can relate to personal experience wrt poor drainage of my plot and, had I known about the extreme waterlogging which takes place every winter, I think I might have aborted the purchase. I am aware that a few of my neighbours installed land drains at significant cost and upheaval. As a pensioner, existing on a state pension plus a laughably small annuity, installing a land drain is definitely a 'no go'. From late Autumn onwards until April or May my lawn walks like a thick, wet sponge:
mud actually 'seeps' up through the lawn and spreads like butter as soon as you walk on it - not pleasant.
Any comments/answers would be welcome. :(

Nearlyman