Sometimes the logistics requires that the towpath move from one side of the canal to the other - swampy ground, rocky outcrop, buildings etc. In that situation going under a larger bridge doesn't solve the problem.
Maybe a tax dodge. Rental income from the house or capital gain from its resale will be taxed at her no-other-income bracket rather that at dad's presumably higher one.
*sigh*
https://www.reddit.com/r/MapsWithoutNZ/comments/9y3mov/maps_almost_without_australia/