Genuine question: at what point is allowing a baby to sob, uncomforted, so they eventually fall asleep in the hopeless conviction that nobody will aid or soothe them, acceptable, let alone "in their best interests"? Because coaxing to sleep and seeking to extend sleep periods is what all parents, routinised or not, do. Nobody likes being sleep-deprived! What varies is the point in time at which we start to exert authority on bedtimes in the face of distress. You can gussy it up all you want: that's the reality of the dispute here: when you prioritise your own sleep, even in the face of a crying child.
I have never left a baby of mine to cry until and unless they were old enough to know where I was, why I was doing it, and that they weren't abandoned - just expected to get sufficient rest. And, necessarily, that was a toddler, not a baby, and one old enough to get out of his toddler bed and scuttle through to me to protest/be returned firmly to bed. To compare parents who don't want to leave infants to sob with those who can't be bothered to teach their children about healthy eating, sharing, and not hitting is simply ridiculous. From a logical standpoint, you can't teach those things until a child has the capacity to reason; a failure to teach your children those things once they're old enough is simple bad parenting. But the analogy makes sense to me in this at least: would you try to teach your 3 month old to share? To not hit? To eat healthily? You can't. They lack the developmental readiness. And I personally think expecting a tiny baby to go against its biological programming and then pretending it's for the best interests of that baby... I just don't agree. It's for the benefit of the adults.
Do you seriously imagine I wanted to get up with my son through the night and then when he rose at 5.30 to start his day? Bluntly, there were times I longed to just leave him to cry himself back to sleep so I could get more of my own, but I felt conscience-bound to attend to him in the brief point in his life during which he was unable to understand/feel safe if I didn't. That's the bottom line for me. I didn't think the fear and distress of my child was okay. (I also appreciate that many women who use routines also feel that way and never leave their babies to cry uncomforted, in which case, I think the argument is about semantics - we're parenting the same way under different headings.) I accept that's my own moral code, and I don't expect others to share it, but there is, to me, a comic element in women who choose a parenting pattern on the grounds they get an easier life out of it trying to compare those of us who don't to parents who allow their kids to clobber, eat junk and toy-hoard. Not sleep-training is harder, if your child isn't a natural sleeper (and if they are, then you don't need to sleep-train). That's something all those who sleep-train say for themselves, when advocating it.
And my 5 month old was out in town with me and my son from 10 am till 6 pm today. She remains exclusively breastfed. I just fed her in a quiet corner, when she was thirsty/hungry. Which was on three occasions, as it happens. Can't fathom why that is seen as difficult - was far more of a palaver tending to DS, who needed bottles.