Ooooh, we should talk about a thing. Here, take a look at this.
These hearts use the exact same yarn (they’re from the same skein of sevensistersarts’ Matrika base), but two different sizes of needles. The top one is knit on size 1 needles, the bottom one is knit on size 00 needles. See how different the fabrics are?
That bottom is a solid 11 stitches per inch, the top one is more like 9 (it’s hard to tell exactly because it’s not blocked yet, and being on the needles distorts it a bit and makes it hard to measure). See how different the fabric looks? How much more tightly the yarn is held in place on the bottom one?
Now, this isn’t intended to be sock yarn (it’s a bit thinner and a bit more softly structured than classic sock yarn), and we’re not making socks, but this actually shows you something you should keep in mind when you do knit socks.
For socks, you want your fabric to look more like the bottom heart, where the stitches are smushed up very very close to their neighbors and the yarn has almost no room to move about.
You probably won’t be knitting your socks at 11spi (and again, this isn’t intended to be sock yarn, so absolutely nothing I’m saying is in any way a criticism of the yarn, it just offered us an interesting example to discuss fabric structure), but you do want your stitches to be firmly nestled together with very little space between them. For a classic sock yarn, that might very well be something like 9 or even 10 stitches per inch. I get a bit daunted knitting that tightly, so I tend to look for heavy fingering weight or even sport or dk weight yarns to do socks with, and there you can get away with something closer to 8 stitches per inch. And sometimes I make delightfully cozy socks with thick yarn at more like 7 stitches per inch.
The actual, specific gauge (10 spi, 9 spi, 8 spi etc) doesn’t matter as much as the structure of the fabric (well, it matters for picking what size you make, but that’s a separate issue). The density of the fabric is what’s important. You want that tight, firm fabric that will stand up to being walked on. That’s how you make your socks last for ages.