Actually, Opera can use a (Opera operated) proxy to scale the images down, compress html, css and js. This feature is called "Opera Turbo", I think, and is unique to Opera (browser and company) - at least as a built in from the start.
The second reason is Opera Mini, which can run on "dumbphones" and is a fast, modern browser, which can use "Opera Turbo" too. People there didn't have access to newer hardware, stuck with "dumbphones" were essentially abandoned by everyone else - only Opera was there for them.
Third reason was Opera's good support for cryptography, which is nice to have when you know every byte you send is archived and can (and will be) used against you if you happen to become inconvenient.
So, to summarize: your summary is inaccurate, misleading and not necessary.