Hi rover,
In some instances, I find that comes in pretty handy...
If I've had a long day, for example, and stop late in the day or at night, and there's no need to put the sailcover on for the night. If the conditions are calm, I might simply tidy up the flake of the sail, and leave it 'cradled' in the lazy jacks until it's time to hoist again the next morning...
More likely, however, are those situations where I know I'll be hoisting the main in close quarters, where it needs to be done quickly, upon leaving a dock or anchorage. By having the jacks deployed, I can attach the halyard and remove all the sail ties beforehand, and have no worries about the sail falling off the boom or otherwise getting blown about and getting snagged on deck gear, etc... Then, when I do get to the spot where I have the time to hoist, it's very quick work for me to move to the mast and raise the sail, and be on my way... And that's where having the jacks led outboard to the spreaders really works for me, giving me a bit of leeway if the main is not absolutely head to wind during the hoist...
Once I got my setup properly adjusted/positioned, I don't think I've ever had a batten snag during the hoist - although full battens obviously somewhat less prone to doing so...
best regards,
Jon