I was wondering if this was simply game design or a glitch. It seems that I have only been able to unlock maybe 4 or 5 lunch boxes. Now it is simply caps, I am curious if that means I can no longer get lunch boxes or if they are simply show up later on.

Now I am curious does deleting a vault mean they are gone and I can no longer unlock them through challenges? If not and I can indeed unlock them again when I start a new vault, do you think I can unlock them in later when the more challenging challenges show up?

If this is the case then I don't mind working for it. I just hope me buying with real money isn't the only way to unlock them after awhile.

I'm assuming that lunchboxes are mainly meant as in-app purchases (like gems or stuff like that in other games). In start you get at least 3 pretty soon and probably some you'll get time to time when comes challenge with lunchbox reward. Each vault have separate account with lunchboxes and stuff and deleting vault you getting rid of their lunchboxes and stuff, but new vaults will get same chance of lunchbox challenges.

you can get more lunchboxes later... they show up randomly at times.. at one point i got an entire group of challenges with every one of them having lunchboxes as rewards and then awhile later another one showed up (this was all later in the game at around 30 dwellers) so they can show up again.. but the first 3 are guarenteed early on.

Seems to me they're just infrequent.

Yeah it's totally random. I have two objectives at the moment that will give me a lunchbox. I did buy 5 Lunchboxes but two other save games I have I've found rare weapons and Dwellers from the cards without buying Lunchboxes.