“שמרתם את המצות is a פסוק”
The above pertains ONLY to the Matzos you are Yotzei, otherwise CT has a good point it is a Chumrah.
Personally, I think people are just confusing the first days with all the rest.
Especially with not eating Machine Matzos, unless you are from the ones that see it as Chametz, (as per Devrei Chaim of Sanz), otherwise the main conflict (if you read thru the Teshuvos) on Machine Matzos was whether you can be Yotzei the Lishmah etc as per the Mitzvah.
“Just to elaborate on what laskern wrote earlier. The Shitas HaGr”a is that Matza, besides for the seder night/s, is a mitzva kiyumis”
The GR”A is not like Shu”A and all other rishonim. (There is a Chazkuny that upholds so). In any case, you can eat ONE kezayis each day and you are fine. The rest can be from the above especially for kids…
BP – “In Europe most people ate non Shmurah Matzah (except for the sedorim). I heard from someone old enough to remember that in Munkatch there were 7 Matzah Bakeries
See below informative link from the Munkatcher how it was done in his times (and the shitas haGR”A). Many didn’t eat any Matzos all the rest of the days:
http://www.hebrewbooks.org/pdfpager.aspx?req=4751&st=&pgnum=224
Also, see Sdei Chemed regarding eating Matzoh as per shitas haGR”A – he quotes a minhag (i.e. Am Haratzos) some had to recite a bracha all seven days
http://www.hebrewbooks.org/pdfpager.aspx?req=14155&st=&pgnum=403