tl;dr: Companies have a limited budget of "innovation tokens" to spend on novel technology, so most of the stack should be boring, well-understood tools (MySQL, Postgres, Memcached, cron) whose failure modes are known. "Best tool for the job" thinking ignores the massive long-term operational cost of adding new tech; you should optimize globally and prefer solving problems with what you already have. When adding new tech is genuinely warranted, make it a deliberate, company-wide conversation with a migration plan away from what it replaces.