You're asking for a simplified answer to an emotive question op and not expecting to offend anyone.
I'm not having a pop at you for not having had your baby yet but at this point you're all wide eyed about the prosepect of breastfeeding.
To be honest after I went to one of those talks the woman were so invested in promoting breastfeeding (afterall that's what they were paid to do) I genuinely thought anyone and everyone could breastfeed.
The scenarios they gave me in hindsite were ridiculous.
The women running the talk made me feel like was a doddle (oh just co sleep and feed, dream feed, you don't have to do any housework while you're feeding just sit with baby) I was certain without a doubt I'd be breastfeeding and making sure my baby got all these amazing benefits.
But the reality was completely different.
I was resuscitated after having dd, on drugs that meant I couldn't breastfeed and really ill. The midwives were lovely enough to cup feed her for me but when I tried to breastfeed a few weeks later I just got no where, she wouldn't latch properly, she had a physical problem with her mouth, she had an undiagnosed mechanic swallow problem and I couldn't do it.
But because I'd been to that talk where I was led to believe all woman can breast feed I felt like an utter and complete failure for not managing to do so it affected my mental health.
So wanting a simplified answer is a bit insulting to parents who have been through hard times breastfeeding as you cannot appreciate the guilt involved with stopping until you've been there to be honest (sorry if that sounds patronising I don't mean to).
You keep saying you're not asking the Mum's who had a valid medical reason which again appears judgmental to mothers who just decided not to and when woman say because they just didn't want to you pry further because that's not enough of an answer for you.
I didn't breastfeed my second child because I didn't want to. That's it.
Obviously there were elements involved in my decision making process but bottom line I just didn't want to and I knew she'd be fine either way so it wasn't really a difficult decision to make the second time around.
There can be a million reasons people 'who can' breastfeed don't and frankly interested or not, they're not your business.
It's about as easy as asking people who smoke why don't they stop knowing the benefits?
Why don't overweight people just eat healthy knowing the benefits?
The answer is because that's life, everyone is different based on their past experiences, upbringing, values etc everyone has walked their own path and that affects their decision making process.
Personally I don't think breastfeeding versus formula feeding is a big deal in the grand scheme of things but I appreciate some people do.
I think when you're going to make statements about not understanding why the mothers who can BF don't despite knowing all the benefits, meant to or not it comes across as a bit judgemental.
Good luck with the rest of your pregnancy op and I wish you well in your BF journey wherever it takes you.