Sure, if you want a personal homepage, or put up an ode to your dog Scruffy on the internet, tools like this may very well work for you. But in those use cases, we've already had capable tools for years, many of which produce cleaner code than this.
For anything bigger/more professional, dirty/bloated HTML/CSS means a few things:
- Bigger downloads for your visitors, wasting their bandwidth. But whatever, you're not paying for that, right?
- More data transfer for you and your host. That you do pay for.
- Increased latency (sometimes massively) and decreased accessibility for people with slower connections. Given the awesomeness of American broadband performance, that means most of your customers/visitors. More latency = more bounces = fewer visitors buying stuff from you, reading your ad copy, etc etc.
- Increased rendering times. See: bounce rate.
And these aren't negligible effects. The difference between a 10KB and 100KB file is very significant, and you don't need millions of uniques a month to find out the difference.
Dirty EPS files are not the same thing - because unclean PostScript suffers from none of these deficiencies except bigger downloads - which for EPS files has little to no consequence in the typical use case.