Clearly they do care
Let's get this in context. One beekeeper, one year, only two colonies.
I do not have a TBH, but I do run a couple of Dartingtons and maybe a beehaus (next year). They are a half-way house, you might say, between the normal tiered hive and the TBH. Some of my colonies do much better than others. I know that, and I know why.
Yes, manipulations are less intrusive with a single tier hive. The tiered hived bees sometimes do not want their brood nest/hive organisation disturbed, or indeed split in half horizontally. Depends on the strain of bees to a large extent.
The thing is, managed colonies (TBHs or framed hives) are more likely to suffer diseases than natural, or feral, colonies due to the closer neighbouring colonies, and the framed versions are better for checking, although some TBHers will say their system has fewer instances of disease. They may well be the ones with only a couple of hives.
Virtually all colonies are infested with the parasite varroa and a lot/most need treatments/intervention to ensure their survival. Most feral colonies have been killed off by the mite.
Swarming is another issue that some can forget to consider.
Honey surplus can be far greater from tiered hives (Dartingtons are arranged as tiered for just part of the season and could be organised as virtually horizontal hives, if one wanted).
Usually, the beekeeper is a tiered and framed hive beekeeper or a TBH beekeeper. The TBHers tend to claim their ways are superior and often shout loudly about it.
Personally, I subscribe to rae's view. Bees look for a box to live in. Some fare better than others. I like to keep bees and get some return to offset my costs - I certainly don't make any profit from them. I may well try a TBH sometime - not so much different than my Dartingtons, but I might.
The two systems are different, not better or worse, than the other.
Regards, RAB