Lot to unpack here.

Swords were more expensive/difficult to make than a spear, but there were cheap and poorly made vs very well made using the best iron/steel, best hardening technology, etc. And they tended to last. Hence they were very prolific.

Also, what was actually associated with knights and knighthood? Golden spurs is what people from medieval to late rennisance most associated with knights, second the horse, third the lance (especially look at the terms used for knights and those non-knights that were similarly armed. It's literally Lancer in many cases, horseman in others)

The sword gets a boost in relevance because a big part of knighthood was supposed to be vows, keeping your word, etc. The sword was a great stand-in for a crucifix

It's only modern pop culture that associates sword with knighthood. And that's because it makes a much better movie prop than a horse or a lance