As someone who is seeking a partner, I think one reason it is a big thing is because having a loving partner amplifies your goals.
I love travelling. Going travelling alone can be fun, but it is much better if you are going with someone you love. Of course friends can serve a similar purpose, but in my experience it is harder to truly connect with friends (especially if you are a male - something like travelling is seen as pretty 'feminine', so unfortunately it is still slightly taboo).
If you have goals of being financially independent, a partner can support you physically and emotionally, as well as directly help you achieve your goal. Your partner working increases your joint income, allowing you to save more collectively and build a bigger pool of wealth.
In short, most goals/passions are better when you can experience it with someone close. I still enjoy my hobbies without a partner - it is simply even more enjoyable when they are around.