Driving confusion

I understand that the lines for lanes ate hard to see, however the lanes don't change very often.

I often turn onto Days road off of Bath road. I use the outside turning lane because I have a friend that lives in the first set of apartments.

Tonight, like many nights, I got honked at for turning on the flashing green light. My husband saw someone using that lane to go straight lastnight instead of turning. How do people miss a turning lane I've been using for years?