Want to drain/change compressor oil, but there's no outlet
If there's a window, you don't need a dipstick.

If there's no lower outlet, open the inlet and turn it over. Or, suck it out (auto parts stores typically have something for doing that.)

Compressor oil changing does not need to be especially convenient as it's relatively infrequent, and the scale of compressor you show is not impossible to turn over by hand - so, no drain plug = one less place to leak, not "trolling"