Frisson.
Just because you don't see things whilst out and about does not mean its not normal.
Undressing and getting into bed is normal but people tend to avoid doing it in shopping centres.( how ever the bed display in John Lewis has fatten seamed very attractive after a no sleep night)
When you have a breast feeding toddler its not the same as with a younger baby up till about 6 months its quite usual for baby's to just have milk breast or formula after 6 months up to about a year comes the most of nutrition from milk but lets play with food stage but obviously the amount of milk does tend to reduce, after about a year any kind of milk is not used instead of solid food so out and about you tend to see over ones eating solid food and getting in some cup practice.
Quite a lot of extended breast feeders tend to breast feed first thing in the morning and last thing at night because baby's do tend to naturally get into this patten.
Its not being hidden (well not all the time,as this thread has shown some mums get quite upset about people's reactions) its just that its more usual to be indoors at the times your child has milk instead of solid food.
We see tiny babies with boobs or bottles loads just because they need loads of it and frequently and nobody wants to hide themselves away whilst that stage happens so they go out and about but we rarely see other families morning or bedtime routines so we just don't see it,and in all fairness its not exactly the most interesting topic so we don't really talk about it in RL unless its to grandparents because for some reason they are interested in all sorts of boring crap.
Its quite normal and it is also quite normal in the uk for children to be given some kind of milk at that age as part of there nutritional needs.