Reason is simple MDL don't want to maintain it. Neither do they want to be responsible for any accidents on the slipway thereore they closed it. The added advantage for MDL is they can then charge for lifts.
To be honest the public slipway is much preferable anyway
Here it comes again, I don't stand a chance
Soul possession, Got me in a trance
Pullin' me back to you - Deja Voodoo