There's several intersections and driveways in this stretch of highway. So probably to reduce the possibility of cyclist getting hit by cars making right turns.
There should at least be some type of physical barrier between moving cars and bikes.
Why? Sincerely asking.
Back in the day (probably late 70's) the bicycle movement tried build legitimacy by claiming they had a right to the road also. Governments followed this up with bike lanes along roads with cars doing 50+ mph (regradless of posted speed limits). As someone who rides a bike as a means of transportation I don't want to share the road with cars. I would much prefer my own area to ride in. I have been hit 2 times by cars and I have 0 interest in making a 3rd time.
Sadly, the bicycle kabal in this country is dominated by the suburban exercise rider with his $5,000 bike, team kit, and entitlement mentality and wants government to pay for his exercise facility. I just want to get a loaf of bread without being killed.