It's simple, it's worth a few extra bucks to me to buy tins to not have to deal with divvying up pounds into manageable amounts that I'd want to open at any given time, and that I'm wanting to try everything and don't want to deal with trying to get rid of lbs of stuff I might end up not wanting or that might not age well by the time I get to it. For me, tins make more sense, that's it, they're super convenient.
Plus, a 2 oz tin will keep just fine but a 1-2 oz sampler bag from bulk then doesn't get the same level of discount as buying a pound or more of it, then what many aren't mentioning is the cost of mylar bags or jars or whatever, so for 2oz from bulk, you may be saving a few pennies after adding in the cost of something to store it in.
I've had tins bought from B&Ms of all types (square and round) of unknown provenance but known manufacturing dates as old as 4-5 years prior to when I bought them and the seals were still good. Could a seal fail? Sure, but I haven't had one fail yet. That's the risk I take, and one I'm not terribly worried about based on my experience.
You're not missing out by not buying tins, there's nothing inherently magical about them.
But buying from bulk makes sense only if you're buying actual bulk (except cases where something is only sold in bulk and you just want a few ounces). When you get 1-5 lbs in bulk though, then you have to do something for long-term storage unless you only smoke that one blend and smoke so much you'll rip through the whole thing in a month.
And I'm not against buying in bulk, I bought 1 lb each of HH Burley Flake and Navy Flake from Mac Baren. Long term storage, all I did was separate the flakes into 2 oz amounts and vacuum sealed them and stuck them back in their boxes. Is this proper for long term storage? No, not by a long shot, but better than nothing for keeping them. Still took an hour and a half to store up the two boxes. But these are two blends I like that I will smoke a lot of, might be gone within 2 years. Now in this case, this does save space over buying 1 lb worth of tins.