Probably that bees are in decline across the nation (if not the world). Possibly the plants aren't bee pollinated.

I'm seeing a lot of bumblebees but only the occasional honeybee. I'm feeling very protective of my bumblebees and hope they don't suffer the same fate as the honeybees. (In my case the lack of honeybees I'm observing is on tree and shrub blossoms that definitely pollinate via bees. It's very sad. At least the bumblebees are hard at work.)

I'm sorry about your tenant. The world has lost one of its gardeners. RIP

I also find that the bees definitely prefer certain flowers. For instance, I grow a number of clematis, but there is one particular bell-shaped clematis that has more bees on it than all the others combined. I think that many garden perennials have been bred for large, often double flowers, and it may come at the expense of pollen and nectar, things that the breeders aren't selecting for.

However, I also have many more bumble bees than I have honey bees, something that didn't used to be the case, even though the only insect killer I use is Bt which doesn't effect bees.