Why does this happen? Is there some subcontractor who just bills by the piece so they don't care about de-duping the idiotic mailmerge that has 5 entries for each entity I'm affiliated with?
In the ones like Dell (which I've also experienced in the past), I suspect there's some metric involved for getting the most contacts for "coverage". The reality is unless they were tracking my moves to different companies, there could be different people with the same name. In that sense, I'm very glad they can't correlate with employment data.
There's also the idea that sending to multiple people within a company means someone may see something they want and try to go through the procurement process because of the catalog, rather than because "IT" says it's time for a refresh.
Not that I agree with any of those practices, for a number of reasons, but I could understand the case for them.
Putting on my cynic hat, buying lots of newspaper, television and radio ads is a good way to keep the media on the sidelines instead of criticizing the incumbents.