In Unturned the main point for zombies to exist is to give a player loot, Freezzer (sandbox) has no need for that, zombies become completely useless, the primary playerbase only does pvp on these servers while much fewer do other things such as roleplaying, zombies therefore are never needed, when doing pvp zombies often get in the way of shots, give away your position, start hitting you when getting fired at and many more annoying things, other sandbox servers also completely removed them and the whole experience was much more enjoyable. On Freezzer they only get in the way of everything, they were nerfed enough to be useless but still be annoying, it was argued in the past that they could be used to practice aim but most of the time you are shooting players and practicing aim on them, plus they don't move and are not very good for practicing.
If removing zombies completely cannot be done then at least remove horde beacons, they have no use other than annoying people, often they are spammed in hidden places in the main pvp area and it all becomes a zombie mess, anything a player is doing has to be interrupted by zombies, usually there is more than 1 placed so even if a player finishes the horde beacon they just come again, the cooldown for them doesn't work either because a player can simply save lockers full of them on a vehicle and reload it or just craft them so even if the beacons are found the player which placed them will just do it again right after. Adding to that horde beacons also cause more lag to the server and for some players it can be a big issue and turn off point.
Thank you for your consideration