I guess it all depends on where you like to put stuff in your bag; the main compartment is where all the "important" things go for me, and with no proper closure? Nah, not happening! I'd only put a pen or lip gloss there if I owned a PTTM! So, what a waste of space.
Honestly the other Natashas (like the Classic Q, for example) have at least a magnetic closure; there doesn't seem to be any rhyme or reason the PTTM is lacking for it...except if they were wanting to make it ~different~, lol. It just seems odd IMO. Oh well, I'm a practical person at heart I suppose!