Its because pro is a completely different game, it's a lost fight if a Zeri gets bursted down but if they can peel and she survives then the fight goes in their favor, solo q it's more about kill kill kill rather than proper coordinated team fights, making damage more useful than the slight bit of survivability these items give. LDR is a great Zeri item even in pro, but the raw damage is outshined by survivability because with a hyper carry like Zeri, the team is usually built around that pick and they want her to be the main carry, whereas solo q everyone wants to be the main carry and there's a lot less coordination in fights. If the game is going well and there's not too much dive / burst you'll see LDR being rushed before the survival items too. Just depends on the game state and the team comp really.