If you have no libido, you have no urge or desire for sex. No more fantasizing about sex, heart pounding excitement when it comes to sex/girls, butterflies in stomach… its like looking at a plate of delicious food, but you’re not hungry. Lust has been drained from your body and you are simply not horny.
Loss of libido doesn’t mean that physicallyyou are unable to acheive an erection via manual stimulation, or that there is anything physically wrong with your penis. But libido is important for non-contact erections to take place, in anticipation of the act itself, as one gets “turned on”, and to help maintain the erection during sexual activity without manual stimulation (if one has no mechanical problems with their penis, ie bloodflow etc).
Guys with raging libidos and erectile dysfunction likely have an organic, physical problem with the penis/erectile mechanism… bloodflow issues, decreased nitric oxide production, tissue changes from smooth muscle to collagenous fibres etc. This could be due to androgen deprivation (ie, DHT) from drugs such as Finasteride. In these cases, drugs like Viagra can help – you are already horny, you just can’t phyiscally obtain the erection as easily as you normally would. This is a big difference compared to having no libido, which usually drives the erection in the first place.