To tell you the truth, I’m more concerned with the fact that for the past 30 years, Peach, a princess (or so we are told) is wearing the same outfit. It reflects heavily on her reign as... ahem… princess?! Where exactly are the queen and/or king? Where is her court?
For a kingdom with mostly animals and fantastic creatures, one must ponder the need for so many pipes laying around, especially when all of them are open, don’t lead anywhere, and with some being home for carnivorous plants. Perhaps the lack of sanitation is why Peach needs a plumber on-hand.
Even if we consider Bowser gender (or lack thereof), one must question their mental stability or the way Bowser taunts Peach, the assumed lover, with all manner of BDSM that peach may or may not approve and the not so frequent visit that they force on her. Every meeting needs to be accompanied by explosions and grand kidnapping plans, disregarding the kingdom financial crisis and the need for a monarch to handle all the day-to-day decisions.
As for Mario and Luigi, I would agree, if not for the lack of sexual tension between the two. They seem to just fill their days with rescuing Peach, instead of actually do some plumbing. Perhaps she is their only customer — which might explain all the pipes laying around — or they might be so inept in their job as to actually finance all those kidnappings. I smell some collusion between the brothers and Bowser.