Abandoned Dead Coins are one of the most common dead coins or the most common, this is for a number of reasons. If a coin or token has little information on why it died it falls into the default abandoned classification.
This is to not tarnish the developers reputation as there are some legitimate reasons coins get abandoned. For example the developer died, health issues or family issues while working on a project. We mention that in the affected projects.
Loss of traction
Over time coins can lose traction and just slowly fall down the rankings. Some updates are made but the coin keeps backpedalling, this can be due to a outdated blockchain or algorithm. The coin ends up dead.
Removed from exchanges
Coins commonly get removed from exchanges by not meeting the criteria, this can be low volume or wallet issues. Or even security flaws. This is very commonly with low volume coins that have slack development.