It amazes me that to this day, furries do not understand sexuality despite obsessing over it.

It is correct that the seminal vesicles produce a majority of what eventually becomes semen (which some of you don't seem to be able to differentiate from sperm), the amount being estimated from 60~70%. I may remind you that is barely more than half and will certainly be noticeable if missing.

However, the seminal vesicles cannot function - or indeed develop in the first place - without androgen. The most important androgen is testosterone, which is largely if not solely produced by the testes, and all other androgen is produced in smaller amounts to support its function.

A lack of testicles will cause a sharp drop in androgen, which will cause the seminal vesicles to atrophy and stop functioning, alongside other major and potentially fatal health conditions. On the plus side, testosterone is also known to weaken the immune system so I guess there's that.

The point is, the testes are indeed responsible for the great majority of male ejaculate, though not directly.

But hell, in the end that doesn't matter, the reason balls should be present is simply because a cock with no balls is disgusting and incomplete. Everything with a cock should have two balls, both external, no more and no less. To do otherwise is mutilation and madness.