It would be nice to get update for jquery library currently we have 1.9.1 which has some security vulnerabilities and we cannot choose not to load the library in our web app.
Web apps are simple JSSP with added codes from XSL templates such as web-webApp.xsl and web-core.xsl. you may find more about web apps generation in this blog post.
For example, "xtk:form/web-core.xsl" contains at line 124 the following jQuery inclusion: