Please Explain Something To Me

Why is it that a person will work their tail off for their job, to get a promotion, or to achieve any of  their goals, but they won't put any work into a relationship? Why is a promotion worth effort but a person who could love you isn't? Where is that promotion going to be if your company goes under? If you are an athlete and hurt your knee, then there goes that career. Why is that still worth more than a life-long partner? Who decided that relationships are supposed to be easy? What happened to anything worth having taking work? At the end of the day, isn't a person who could share your life with you worth even more effort than all those other things? Sure, some relationships are shallow and fleeting. Those aren't worth effort. But when someone shows that they want to be by your side for the long haul and they enrich your life, then they should be precious to you and worth all the effort in the world.