I am guessing but it may be related to the type of flower. I have a variety of flowering herbs and flowers growing to attract beneficial insects. I don't have oregano, but I do know that honey bees have short tongues and cannot reach the nectar in deep throated flowers. They prefer small relatively flat flowers or funnel shaped flowers with a wide throat. There are no bumble bees here, we do have carpenter bees. The carpenter bees like the purple flowers of verbena and lavender. They also have a habit of cutting through the side of flowers like honeysuckle to get to the nectar.
Honey bees like sunflower and other composite flowers like asters, single zinnia, single marigolds, and calendula. Shiso, hibiscus, fennel, dill, basil, alliums, honeysuckle, citrus, avocado and other flowering shrubs and vines are visited regularly.
The honeybees visit a single source until it is exhausted, so they visit my basil year round because I allow my basils to bloom year round. They usually don't hop to another source once they have found one too often. They do like corn and palm pollen though. Often it is a case where the bees have to locate the source. They can travel up to 5 miles to find food but they would rather exploit a source nearby. We also have hives and 30 acres for them to forage so they stay close to home. Although, they do visit home depot next door.
I have alyssum, honeysuckle, and penta and I see bees on them all of the time, while others have said they don't see bees on those flowers. The nectar on alyssum and penta are hard for the short tongued honey bees to get to and they are more suited to the longer tongued carpenter bees and butterflies. They will still visit to harvest pollen.
I have also noticed that the carpenter bees and honeybees may forage in the same area, they usually don't forage together on the same plant at the same time. Carpenter bees and honey bees usually don't visit sunflowers at the same time but they may visit minutes apart.
In some places honey bees either have swarmed or are getting ready to kick out the drones and cluster. There will be fewer bees during winter and cold and rain will keep them in the hive. They will only go out to forage on nice sunny days if there is forage available.
Our bees have forage year round so their cluster does not get as small as other beekeepers with less winter forage and we do not usually have to feed our bees even though we will rob them of all but two full frames of honey. The reason for this is because the 30 acre garden will normally have something in bloom they can forage on when it isn't raining. Rain and strong winds do cause problems because then they cannot fly and stay in the hives and eat honey. Strong hives will rob weak ones and if the honey runs out, they will all starve together.
Happy gardening in Hawaii. Gardens are where people grow.