adcs do need mobility, for the simple fact that if you're not positioned correctly you're dead, look at like 90% of the adcs in the game, Kalista - passive, Lucian - E, Graves - E, Tristana - W, Ezreal - E, Vayne - Q, Caitlyn - E, Corki - W, Draven - E, Jinx - passive ( while she doesn't have any initial mobile ability, she does have her Q which increases her ability to kite and reposition ) Quinn - R and E, Sivir - R, Twitch - Q ( now this ability is a rather unique one, it doesn't give him an instant invisibility anymore but it still does give him escape potential and the ability to reposition ) even Teemo who i don't consider a marksman but riot does has a mobility ability his W Move quick.. just so you know, the adcs that don't have mobility are Ashe ( who can slow/stun her targets ) Miss Fortune ( who has a passive to increase her movement speed until she is hit by a champion ) Kog'maw ( who explodes after death and has 2 abilities with extremely long range ) Urgot ( in my opinion Urgot is one of the worst adcs in the game, based on his low attack range, and his ult positioning him in the enemy team most of the time, and due to his low mobility ) the last adc that i haven't mentioned is Varus.. we all know his issues, hence why we're here..