The easiest explanation for Colin Kaepernick's extended stay in the unemployment office would be pointing to politics. He refused to stand for the national anthem last season in protest of racism and police brutality, became the focus of a national controversy and scared away NFL executives in charge of building rosters.
It's a neat and clean theory that's easy to comprehend. How else could a quarterback who started for the 49ers in the Super Bowl four years ago be left in the cold while Mike Glennon signs a big contract with the Bears and former Bills bust EJ Manuel lands a new gig with the Raiders?
Execs make decisions for various reasons, including the potential for headaches. The Bears wanted a drop-back passer and signed Glennon. The Raiders looked to create a competition for the backup job and gave Manuel an opportunity.
Kaepernick has been in steady decline for years. He has accuracy issues, plays a style unsuited for most NFL offenses and draws unwanted attention. Many teams will overlook off-field issues if players perform on the field. To me, it looks like GMs added up all the variables and came up with a net loss.