In recent years with the growth in 3840×2160 panels, games have grown in size with increased level of details in the game artwork.
There are now 2 games that are over 100 GB and 11 games that are over 50 GB in the Steam collection. This pressures the need for more storage generally. When the rest of Halo: MCC is delivered, that will likely move it into the 100GB group. It is also known that Halo 5 is 125 GB on the console and there is indication that it will eventually become available on Steam down the road. Halo: Infinite is about 50 GB and runs on the Xbox One so the game will have easy system requirements.
The existing Intel 660p 512GB SSD can handle a few large games before it runs out of room. Larger capacity SSD drives are available but the cost rises exponentially. Consoles are shipping with 1TB SSD storage. The options for the PC now span to 4TB for the M.2 format.
The Sabrent Rocket 4TB is currently $850, back in November 2019 it was only $650 so already pricing problems are evident. The Sabrent Rocket offers sequential read/write speeds of up to 3,450 MB/s (read) and 3,000 MB/s (write) making it fast enough to almost saturate the PCIe speeds.
High capacity hard disks can handle game collections, inactive games or ones that are seldom played can be kept on a hard disk while the active games can be kept on the SSD. The existing pair of Seagate 4TB disks has managing to handle the game collection. Seagate recently added 8TB disks to the offerings which are desirable.