What about people who want to use several programs on one computer, possibly even written in different languages? This idea is ridiculous unless you think everyone shares your dream of running everything in a smalltalk image.
I don't think everyone shares _my_ dreams, which mostly don't involve Smalltalk images, but this seems quite feasible. And, from experience, making languages interoperate is a hassle, so "written in different languages" isn't all great.
In the particular case of Smalltalk, the operational(?) semantics of which are specified by a virtual machine, one can just compile targeting the virtual machine. c.f compiling Smalltalk and Java to the Self virtual machine, or all the compilers targeting the JVM nowadays.
