Unfortunately this building is really too small to be used as a dwelling, with no room for meaningful expansion and no road access (although the latter hasn't prevented the next one down at Ganny Lock being turned into an attractive house). Any disused building, especially in a semi-urban area, is bound to suffer, however solidly built (and this one is) - I don't think this is a modern phenomenon. Size is no protector, either - the large (Georgian) building by the basin at Brighouse has been going downhill for years since it was abandoned by the local angling club.
The good news is that the lockie's house (a substantial two storey building) nearby has now been refurbished and is occupied (by a boater!) after nearly suffering the same fate.
As for the old river lock at Brookfoot, I was amazed that the river, only a few feet away, didn't inundate the canal here during the floods a couple of years ago, as it did at several points both up and downstream, flooding Dr Bradley's allotment and the Collier's Arms, and hoisting a narrowboat onto the towpath near Shepley Bridge (incompetent recovery of same shown here in a recent thread)
Mac