Sure, some people don't. As Smol Nozomi noted, they can perfectly be content to either live in solitude, as bhikkhus or monks, or something along those lines. Those are however a slim minority. The vast majority of people across all ages and cultures seek partnerships for life.
Ideal gf memes are just that, idealisations. I doubt that many people unironically expect their potential partner to resemble some perfect imagination. I'm quite confident that most people looking for a significant other are ready to compromise and settle for a less than ideal partner – after all we all have our faults and weaknesses, and if we were too picky about everything in life we would come to nothing.
A cat or dog seems like a poor substitute for a significant other. Sure, it might give you a semblance of companionship and genuinely love you, but its more like taking care of a toddler that will never grow up rather than living together with another, equal person that you deeply care about, that cares about you and with which you can share your experiences in life, to which you can offer support and find solace in troubling times.
Also, as Sanakan pointed out, at some point you might ponder the "is my life even worth it?" question. That is to question what you live and work for, what for you put effort into anything you do. To consume and satisfy one's own desires in a hedonistic sense is hardly fulfilling, and most people don't have a passion project or amazing career from which they can draw self-affirmation. Having a partner and family to take care of can be a good motivator for people to keep on going, since they see they're working towards the well-being and growth of their loved ones. What can a forever-alone work towards?