Good reasons for me:
I always wanted kids. No ifs and or buts. I always wanted to be a mother.
Kids are fun and funny. They make you laugh.
They're adorable when they're asleep.
It's fun to teach them things.
Chasing after them can keep you fit (if you don't stress eat from anxiety and lack of sleep).
It's fun to see the world through their eyes, nature, holidays, Disney World, etc.
Having kids and breastfeeding is what women's bodies are designed to do, and it's healthy to nurse for years to delay return of menses. All that estrogen bombarding your body if you never get pregnant or breastfeed for at least several years (cumulatively) makes you more likely to develop reproductive cancers.
If you like to cook big meals, you'll get a daily chance to do that. (If you don't, you'll spend a fortune on feeding them.)
If you love to clean a trashed house and do laundry, it will never stop. (Some people do love to clean, I've heard.)
Reading them stories is fun. I love that. (Nowadays I read out loud to my partners though!)
Cuddling them to bed, while nursing them, feels blissful. (It's hormones, but it feels like love. Okay, it's both.)
At the end of the day, when they're in bed asleep (at least they'll sleep for two hours at a time, maybe) it feels satisfying, a job well done to have kept them alive another day.
It's character-building. The main thing I learned was patience.
It's fun to introduce them to movies you loved as a kid or discovered as a teen (for me, it was Wizard of Oz for littles, and West Side Story for young teens... wow, it was exciting to see them see those for the first time. Of course, then we went on to watch Wizard of Oz, Little Mermaid, etc., 500 times each...)
Those are some good things I experienced. Currently both of my adult daughters struggle with mental illness, despite all the effort my ex and I put into parenting and supporting them to be their authentic selves. The brain is a very fragile and unpredictable organ. Some kids can be raised as shitty as can be and turn out great. Others can be raised with all the skill and love, patience, care, endless sacrifice, money spent on enriching their lives, and end up drug addicts, or even worse.