The point is: most of these applications (say, Photoshop, Gimp, Eclipse, OpenOffice, probably others) are things that you load once to work with them for a couple hours, and don't mind when they consume a lot of your system resources.
If you look at web applications, Google's music app ("My Music" in Google Play) uses a load screen (complete with progress bar) because it's seriously bloated, while Amazon's Cloudplayer just loads and does its thing (which is, playing music).
Needing a load screen is a sign that your app is not, or aims at not being, a Web app anymore - in the sense that you'd also want to loosen the other restrictions - give it its own window, possibly have local file storage or FS caching, etc.; In that case, something like TideSDK ( http://www.tidesdk.org/ ) may come in handy to deliver a desktop app to power users that is based on the same codebase. And, maybe you'd still want a web app that is functional and lean. (As an example for two apps with non-identical possibilities, Google's My Music allows you to change song metadata on desktop browsers but not in the Android app - yet another sign that My Music is meant as a desktop-y app).
In many cases it can be a sign of hubris or lazyness that you cannot get rid of the bloat. Be real and think whether your users actually enjoy waiting that time, since they'll be doing it more often, on machines with less resources and/or slower connection, than yours.
