The Walking Dead’s TV universe was pretty faithful in bringing The Sanctuary to life.
This barrier is not only for protection, but many of those suspended walkers were people that crossed Negan and the Saviors, so it’s more of Negan’s mind control games.
It’s basically a big factory, which offers up plenty of interior space for the tyrannical leader and his flock to survive, and the exterior is surrounded by not only a big fence, but a wall of still-hungry walkers held up by stakes, sticks and chains.
Negan is a villain with a personality as big as life, and so it makes sense that he would take refuge in the kind of shelter that is also extremely daunting and intimidating.