I can't speak about US and Canada, however outside of these markets, it's nearly almost a suite upgrade.
If they don't upgrade you proactively, just ask. Usually it's enough. If not, insist.
If there is still no suite upgrade (suites being available, of course), complain to HH support. They will issue a points compensation. But that's rarely necessary, really.
Once again, this applies outside of North America.
If someone says that Hilton doesn't upgrade Diamonds to suites, it just means that that person travels exclusively within North America. I genuinely feel sorry for North American travelers.