I'll bet it was easier than hunting down the invisible bugs from mixed tabs/spaces or introduced by your editor mangling indentation while moving bits of code around.
Which is easily solvable by setting spaces-for-tabs in your editor (and which I do when working in Python, ... or Java... or C/C++... or pretty much everything because that really solves a whole bunch of issues.)
And violations of spacing/indentation rules are trivially caught by with automated testing/CI, which I do with Jython... or Java... or even C/C++ .... or pretty much everything whenever possible because it is the sane thing to do.
I've only been doing Python for 2 years, including C-to-Python bindings using Python 2.7x, Java-to-Jython/WLST integration (with Jython/WLST being based on Python 2.2), and a tiny bit of Windows automation with IronPython.
Most of my background is Java for enterprise development and C/C++ for embedded/system-level development.
As such, I initially I stumbled across some of the nuisances with Python, the spaces, the lack of a stack trace on exceptions, or the fact that exception hierarchies are slightly, but oh-so-different between Python 2.2 and 2.7. But past those stumbles, I simply use tool configs, procedures and coding standards to deal with them.
And that is the same when I do Java or C++. Each has their own gotchas and effective Java/C++ developers simply do the same - use tool configs, procedures and coding standards to deal with them.
Why would anyone mix tabs with spaces. Use one or the other, regardless of whether you do Python or not. If I see a code base in any language that has that shit mixed up, I know I'm bound to find some other stupid shit in the code.
Why? Because mixing tabs with spaces all over the place, like spelling errors, lack of meaningful comments and/or deeply nested code (arrow anti-patterns), these are all proxies for bad coding practices.
I originally found Python indentation rules to be annoying. After all, how hard is it to auto-indent from an IDE or a command line (or force an auto-indent of code before checking in, or en mass before merging back to the trunk)?
But you know what, people are idiots, and I've learned IN GENERAL not to expect them to write clean code (nor tell clean code from apple pie.)
It is still possible to write horrible Python code, but it is a lot harder to do so in it than in Java or C++ or C#. I would still have preferred to see Python having start and end markers for blocks (a-la begin/end or curly braces) on top of indentation rules.
But it is still a good compromise. Hard to see where code blocks end? Increase indentation. Better yet, refactor that shit out. If I see I have a harder time telling the end of a block, chances are that block is already large (time to refactor out), or that there is a lot of code around it (time to split it into better levels of abstraction).
You know, the kind of stuff we are supposed to do in any language anyways.
Besides, accidental violations that render Python code invalid, those things are trivially solvable by doing shit we are supposed to be doing anyway (namely, avoiding mixing tabs and spaces, automated testing, keeping code small and at least dry-run your shit before committing it to source control.)
I'm not saying programming in Python is Nirvana (for some things, it truly sucks.) But some of the things people complain about, they are just asinine complains for shit that broke because, on a fundamental level, they are not following good industrial practices IMO.