PD replacement for boots

I don't know why people don't sell their Berk boots late game, you sacrifice few movement speed for 25% atk speed and 35% crit, I always do this on ADC once late game every game. PS League's hyper carry , Baron buff- around 550 AD, 2.5atk speed with youmouu/stealth proc, 100% crit, True damage dot with expunge AND 1K+ AOE crits. That's a hyper carry not a vayne nor a kog maw.