That's why. Sony simply launches more new IPs than Nintendo and Microsoft combined.
Also Sony usally puts more money into new IPs. The order, Horizon zero dawn, detroit, Bloodborne, death stranding, ghost of Tsushima are all big budget games that are comparable to their big franchises. They also have smaller new IPs like astro bot, Concrete genie, etc, and that all adds up.
Nintendos biggest new ips this gen so far were arms and astral chain? They obviously aren't comparable in budget to nintendo's big franchises. Splatoon was the last big new IP.