The reason for that is because your definition of normal hosting is shared. (On a dedicated host you can run both PHP and Ruby; and they're roughly the same in terms of getting set up.)
In terms of actually finding website hosting for an application?
Saying PHP is the hardest was likely an over-exagguration, but the market for Heroku PaaS style hosting is growing massively and its Ruby runs on it very easily.
Its not hard (at all) to find hosting for either, the only reason in my mind PHP is harder is because of how beautifully PaaS works and that its free for small applications (good luck finding a reasonable free php host -- I know they exist but you'll have to dig through a whole lot of crud first)
The HN crowd is biased in favor of dedicated and virtual servers. But a very large number of mom-and-pop web pages and small business sites are still hosted on shared. That's what normal hosting means to a lot of people, and it's a market that developers of popular tools (like Drupal and WordPress) can't ignore.
In terms of actually finding website hosting for an application?
Saying PHP is the hardest was likely an over-exagguration, but the market for Heroku PaaS style hosting is growing massively and its Ruby runs on it very easily.
Its not hard (at all) to find hosting for either, the only reason in my mind PHP is harder is because of how beautifully PaaS works and that its free for small applications (good luck finding a reasonable free php host -- I know they exist but you'll have to dig through a whole lot of crud first)