My previous employer I thought had a very practical dress code and the president/CEO set the tone! His daily attire was an untucked collared shirt, jeans and flip flops. Shorts were allowed too.
BUT...
If we had a high profile investor/client visiting our campus then a company-wide email was sent out a day or more in advance to tell people to dress business casual for our 'guest'.

It worked great and those who wanted to dress nicer did so.

The culture that was cultivated by the leadership at the company was one that recognized accomplishments not how spiffy someone dressed.

I've seen dress codes take on a life of their own to where a persons skills, accomplishments and value to the company accomplishing it's core function were completely ignored. I certainly don't condone slovenly or inappropriate attire but dress codes should serve a purpose that enhances the business not just become another rule to be enforced.