If you start following the consequences of the existence of any profession or product to the logical conclusion you can come up with some surprising things. Which is probably why such a tax scheme would be fairly unworkable in practice and would incentivise industries to introduce unnecessary training or overcomplicate their work.

In the case of web startups you can go from "college students all have smartphones so let's build a social network for them to share their most banal thoughts" to "almost everyone in the US will have a smartphone within 5 years and a social networking profile, how can we use this information to provide more efficient public services?". So frivolous spending can accidently create opportunity for much more valuable work.