It is in my eyes worth to add a bit to what others already said here especially considering the comment:
A property list can also be constructed without keyword symbols. Like (base-directory "~/org/" base-extension "org"), so what's the advantage of using keyword symbols if both keyword and non-keyword symbols can solve my problem? Being nice and neat isn't convincing enough for me. –
Searene Jul 23, 2020 at 13:12
@Searene : as good as any programming language is "Turing complete". In other words you can do the same in any language using different means.
What makes the difference between for example Assembler or C and Lisp or Python is the ease of usage of the means the language comes with (usually the more "batteries included" the better).
Another aspect to consider is how good the required and necessary programming style of a programming language plays together with own intuition. The less you need to learn because the things are as you intuitively expect them to be the better.
That said the statement Being nice and neat isn't convincing enough for me. conveys a message about how much your own way of thinking fits to the programming language and the means it comes with.
In other words if your own current intuition plays against accepting that "being nice and neat" (given along with providing examples of usage), there can't be any explanation able to convince you that a feature is useful and makes sense.
But ... what can maybe happen over time is that what you yourself consider as useful and making sense will change and all of the sudden what didn't make much sense before starts to be really meaningful.
All this comes down to "compatibility" of a programming language with own thought patterns.
Finally consider that YOU ARE who gives the existence of a programming language its sense and meaning by using it to achieve this or other effect. Maybe you will find an own making sense use case for these constants playing well with YOUR OWN intuition? And because obvious to YOU but not necessarily to others, having hard time to explain that they are really nice and neat.