I use my Lumia 730 without flip covers and glass protectors and I've dropped it like 5-6 times on a hard floor and it has survived. Don't know how its glass hasn't shattered until now since a few of those drops were screen first. Anyways, here is a thing about plastics/polycarbonate- it has elasticity so in case of drops, it sustains force and don't let it spread to internals. It doesn't even dent easily. And if worst comes to worst, you can always replace it. About screen, you've to get lucky though. Gorilla Glass three coupled with AMOLED makes a good combo though. Even if there are scratches, the screen is usually so vibrant that you never notice them.
But again, if you are sort of a clumsy person, do get protective covers, beauty or no, no phone is prone to damages when it comes to drops. Contrary to what most people believe, metal phones, however beautiful they look, sustain worst damages and dents when they drop.