When running on machines with very low ressources, or on VM hosts with a huge number of VM's memory consumption is crucial.
What | tclsh | jimsh | diet jimsh Size | 4.9M | 3.3M | 481k VIRT | 18840 | 3936 | 960 RES | 8764 | 2220 | 816
In Linux distributions, small shell implementations are used for scripts, bash is common for the CLI, e.g. in Debian:
What | bash | dash VIRT | 9760 | 6124 RES | 2576 | 936
tclsh8.6: 15k, libtcl8.6.so: 1.8M, libc.so.6: 1.9M, libz.so.1: 119K, libm.so.6: 887K, ld-linux-x86-64.so.2: 207K