Actuallly, only the user space tracing aspect of systemtap is dependent on these. You can still do kernel space tracing without them.
We've spent quite a lot of effort explaining the problems with the utrace/uprobes dependency (especially the issues of having to pull the process symbol table into the kernel and of having the kernel actually execute the compiled code to do the traps). There is hope that we might be able to go with a lighter weight infrastructure that simply vectors traps to the user space stap runtime and does all the interpreting in user space. It's just we still haven't quite got system tap buy in yet.