Relationships become too much about control. One person is always trying to control the other, either directly or indirectly. Or one person is trying to maintain control and keep it from the other. Or one person is trying to convince the other that attempts at gaining/maintaining control are not actually what they appear as. Most relationship-obsessed people are actually control-obsessed people and don't even realize it.
Then there is the obligation side of things. Somehow, slowly and insidiously, a list of obligations starts to build. Some spoken, some not. Scorekeeping begins. Did you live up to your obligations? Did he call me like he is supposed to? Did he get me gifts like he was supposed to? Did she come over that night like she always does? Did she put me ahead of her friends when I wanted her to? And it grows. And grows. Some of the worst offenders claim that they don't want control and don't scorekeep for obligations, but on closer inspection, they actually do. Often it's all they do.
When a relationships begins, so too starts control and obligations. In the presence of those, we can never truly perceive or believe another's efforts to do for us (to be with us) are genuine and motivated purely by desire or love, but instead are a calculation of aforementioned control and obligation.
To many, this is stability. Which is what many seek. Stability. That like you would receive from a loving parent. Unconditional love, unconditional support, unwavering availability, unflinching dedication. Everything that attracted you to that person fades and you are left with a bundle of needs latched onto your soul. Feeding. Sometimes symbiotically, usually parasitically. When the two become one, the real trouble begins. All sense of separate identity is lost and a new creature that thrives in the depths of insecurity, loneliness, and neediness is brought forth out of the shadows! The "relationship" has arrived.
Yes, I've been through some experiences that have gotten me to this mindframe. For those I am thankful. I can focus exclusively on myself now. Career, future, money, status. I may even enjoy the company of women along the way, but none of this relationship nonsense.
Oh shucks, do I sound jaded?