RStudio terminal installations not available in Mac terminal

#1

I'm surprised when the behavior of my RStudio terminal differs from the behavior of my Mac terminal.

For instance I recently installed poetry from my RStudio terminal to manage Python projects, and can execute poetry commands.
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I am surprised to discover that poetry can not be executed from the main terminal on my Mac, even when I have the same virtual environment and working directory in both terminals.
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Is there anything about the RStudio terminal that I am fundamentally misunderstanding? I would have thought it's behavior would be identical to the Mac terminal.

#2

I have since confirmed that the $PATH variable was differently defined when I view echo $PATH in RStudio Terminal vs Mac Terminal. I updated $PATH to find poetry, but I am still surprised that this misalignment occurred at all. Why would PATH be different in the two terminals?