Ups staffs their warehouses (or at least did when I worked there as a temp) heavily with temp agency staff who they can toss at any point, they don’t give a shit and while my experience was on the packing side (shrink wrapped bundles, barcode stickers, in store displays) some people did do the shipping side, it sucked and they talked about people throwing things around to meet targets, the quotas were unreasonable, paid next to nothing and the threat of termination was used as a “motivator”, by far the worst working experience of my life and I expect FedEx does the same thing. Met some cool people though so not all bad.