There are so many different superfluous techniques in this game it's not even funny.
If you've been running solid game and this isn't actually a SP, talking about this is like talking about decorating your house while people around you are homeless.
Not that there's anything wrong with that.
For me, lock-in props are primarily for some kind of excuse to talk to her again, or for her to talk to you again. It's a pretty good insurance for a re-initiation after you do a takeaway.
Also great to build jealousy plotlines. Either Mystery or Matador was talking about putting his hat on one girl and telling another girl in a later set to go get the hat back for him.