This is a ridiculous though at the same time completely normal and understandable question and sentiment.
The only answer is that you've only experienced your baby.
It sounds as though you either had a very easy newborn or felt ok about leaving your baby to cry.
Many babies cannot be put down unless you're willing to leave them screaming, which seems a bad idea except when unavoidable because crying is a baby's only way to communicate their needs - they're crying because it's the only way to say something is wrong.
Reflux is common and putting a reflux baby down flat on his back causes them pain, you have to hold them. They grow out of it by a few months or at least by 6 months old usually but of course the sleep deprivation and cold tea phenomenon is real if you have a reflux baby and makes any sleep deprivation described by someone who's baby could sleep flat look like not much worth mentioning.
Also what people find difficult is different.
I blimin loved the toddler years and childminder toddlers - from when my eldest was 11.5 months old until DC2 was born I minded two other babies who's mums I'd met at antenatal classes, so had 3 toddlers born within 6 weeks of each other 7:30am to 5:30pm and remember that time as one of the loveliest of my life.
Dc1 had reflux so was harder at under 4 months than as an older baby and toddler. She also talked very early and very prolifically, which I think might be one reason she only had two tantrums, ever!
DC2 was an easy baby who didn't have reflux, lived in the sling in the days, slept well at night - easy baby. He was an easy toddler too although needed to run physical energy off he actually played alone, which dc1 never did, or with dc1. So easy I thought we could have loads of children and it's be easy, if only giving birth didn't tend to nearly kill me! DC2 had a tricky phase around 4-7 with massive separation anxiety and fear of change, then had an angry phase at 8, but grew out of it and is now an easy young teen.
DC 3 didn't sleep for more than a two hour stretch until he was 3. I can honestly say that I had absolutely no idea, when I'd only had babies one and two, what actual long term sleep deprivation was.