When it comes to cross-browser development, the consideration of JS and CSS3 support, fallback options, workarounds, and degradation all boil down to a matter of time and money. Sometimes, accommodating older or less common browsers can consume a significant portion of your development timeline. As we all know, time equals money. So, is it worth investing this much time in catering to browsers that may not even make up a substantial portion of your website's visitors (i.e., potential customers)?
For instance, currently, even IE8 only holds 4.31% market share. And don't forget, it does support JS.