Cyclists, no bear with me!

What I don’t understand is why on A roads where there are shared cyclist/pedestrian paths running parallel to the road cyclists opt out to ride on the road rather than on the path even when there are no pedestrians but plenty of motor vehicle traffic on the road?

Bonus question the other week a cyclist and me (artic) were both approaching a roundabout, using the same road. He opted to get on the pavement (no one else there, very late at night) - a courteous move, I thought. At the roundabout I turned left, he wanted to go straight but instead of stopping to let me complete my turn he simply dropped on the road and continued to slowly cycle between the curb and my trailer, to my horror. I did anticipate he might do something like that so I had taken the turn wide (indicating well ahead of time) a few feet from the curb. Had I taken the turn as usual (inside wheels as close as possible to the curb) he might’ve stayed on the pavement but what if he hadn’t - it would’ve been 100% my fault in the eyes of the law

Keep cyclists as far away from roads as possible I say, until a kind of test/license is implemented for them so they can share some of the responsibility. I’ll say it again - at the moment it’s like truck drivers are seen as the ‘‘adults’’ on the road and must bear all the responsibility of whatever happens while cyclists are the ‘‘toddlers’’ who can’t do nothing wrong and it’s always the adults’ fault whatever they do