It's all about tradeoffs and maximizing the useful qualities of each.

NVMe storage is extremely fast, but expensive and wears quickly. For a homelab, those drives are usually not easily accessible or replaceable without powering the system off. Internal SSDs are similar with the caveat that they're more likely to be hot swappable when using more server-grade equipment (even older equipment, which more homelabs will have) - HDDs are obviously slower but have higher capacity and wear less quickly. SAS drives will have higher DWPD and more speed for roughly the same (used) cost but you need to make sure the backplane you're using supports them.

External USBs are much cheaper and higher capacity, depending on what you get, but are usually limited to USB-C or even USB3 speeds. Additionally, they can be disconnected physically or via software.

A SAN or vSAN requires either special equipment and cables or a dedicated high speed (10Gbit+) network to function well. There's various free software that can create a vSAN-like thing for you, such as ceph. A "proper" vSAN will be marginally slower than an internal drive array but usually still plenty fast for "big data" which is what it's good for - big chunks of data that don't require the world's fastest drive access speeds. Note that, while unlikely if set up properly, this storage can also be disconnected both physically and via software. Usually this is more recoverable more quickly than USB since common vSAN software will work around this.

For my homelab, I use NAS storage for data that's large, "infinitely" growing, and doesn't need extremely fast access like a database would require. vSAN for most other operations. I should keep local storage or use an actual SAN fabric of some kind but homelabs aren't professional datacenters