Building relationships on Steemit is extremely important as it is in the broader world.
Firstly, human interaction in general is extremely important to our wellbeing. Humans are mainly social creatures who thrive in communities and in an environmemt of cooperation which enables us to complete huge tasks. There is a good reason why you hear the phrases 'teamwork' and 'two heads are better than one' a lot.
Even in computing, multiple cored processors are better than single cored processors, there are examples of this form of interdependancy everywhere, people play to their own strengths and then share.
Steem is no different, we all create our own work and then share it. Share our ideals, loves and lives which hopefully creates understanding and respect on a global scale.
Financially on Steem, making friends and sharing gets you upvotes, which of course are important to earn Steem but more importantly arebthe bo ds of friendship that form which will hopefully make the world just a little bit more peaceful and loving.