[ApK]

Any legitimate marketing messages from a legitimate company can be stopped on request, and the Do Not Call registry limits most of those just fine. Problem is the vast majority of spam comes from con artists, criminals and other shady fly-by-night types, often off-shore, using fake or throw-away numbers and info, who have no intention of obeying any law or request and no fear of being identified and blocked or found and sanctioned (unless you mean "sanctioned" like when that Russian spammer got shot in the head).
Here's more of that "breaking news: water is wet" type info: Criminals don't obey laws.