It is useful so that you can provide advanced functionality to a wider audience to be seen from the web. What if the business user doesn't have the Spotfire client and just wants to view the report from the web? Also, that makes IronPython scripting useless if internal customers can't even view the report properly. My entire company (ConocoPhillips) and your entire enterprise customer base would benefit from this enhancement.
It is indeed possible to run IronPython scripts in the web client for TIBCO Spotfire® on premises, TIBCO Spotfire® Cloud Enterprise and TIBCO Spotfire® for AWS. It is only TIBCO Cloud™ Spotfire where IronPython scripting is limited to the Analyst client.