Marksmen are in 90% of Games for Objectives

Marksmen/ADCs are the go-to class for taking objectives. With high attack speed and DPS, they are the best for trying to take down towers or other structures. There are non-marksmen champions that can take down objectives well like and , but ADCs gain the bonus of range, which outclasses melee splitpushers, and they can use both crit and lifesteal better than any mage could.

Marksmen are reliable for taking turrets 90% of the time (unless you have 's low attack speed) and are able to use range, damage, lifesteal, and sometimes mobility. Not that needing marksmen 90% of the time is a good thing, but it's the most reliable way to be able to take objectives and deal ranged damage.