&gt;<i>Stateless programs; No side effects</i><p>Which is not all it&#x27;s touted up to be.<p>&gt;<i>Concurrency; Plays extremely nice with the rising multi-core technology</i><p>Nice, but not that nice. Don&#x27;t expect any significant speedup for the most common kinds of programs.<p>&gt;<i>Programs are usually shorter and in some cases easier to read</i><p>For some people they are harder to read. As for shorter, Python can be pretty terse too, as can lots of other languages.<p>&gt;<i>Productivity goes up (example: Erlang)</i><p>Anecdotal. In the real world, most systems in production (including at NASA and the most critical environments) are made with imperative&#x2F;oo&#x2F;etc programming, which must count for something. For every WhatsApp there are 10,000 stories of such programs.<p>&gt;<i>Imperative programming is a very old paradigm (as far as I know)</i><p>Functional programming is 5+ decades old too. And parts of math are even older, but we&#x27;re still keeping them...<p>&gt;<i>and possibly not suitable for the 21st century</i><p>Citation needed.