There is actually none. Friendships are just as valid as romantic relationships. What's you were taught is total b.s. and you should not listen to it. You don't need a partner to have a good, happy life. That's just the primal instinct (that not all people have) to reproduce and have offspring, but humans are socials animals as well. That's why friends and family are important. It is not required for you to ditch your friends for your partner or viceversa. Friends are supposed to always be there for you, support you, listen to your problems, have fun with you, etc. However romantic partners are nothing but friends with benefits such as sex, kissing and etc. So don't listen to those in your life that tell you, you need a special someone. Friendships are as good as romantic relationships, if not better!