Originally Posted by FBinNY

The chart isn't about any absolute limits. It's just a guide, highlighting the range for optimal all around performance. The narrower end may offer more precision in steering feel, though may ride more harshly. Conversely, the wider end may offer more comfort, at the expense of sloppier steering (depending on pressure).

In any case, the chart reflects a general consensus among tire manufacturers (not rim makers) about maintaining the ideal Omega profile that's proven itself over a century or more.

So, use the chart as a guideline to find a starting place, then let your actual experience guide you toward wider or narrower section tires, and of course to find the best pressure for the specific tire based on your weight, preferences and road conditions.

FWIW - many tire makers offer tire/rim width charts, and you'll find them to be similar across the board.