Because we've got bitcoin as the main coin.
For me security is a main feature but people over looked it and see it not that important immediately after creation. except when we lost access to it before we becomes more careful or start looking for it. But for the monero I don't really know about.
Security is top priority for most of the systems including these projects. But they won't settle for the best security and what matters to most is the profitability of it. Whether we like it or not, that's how this world comes up with the idea of how good a project is and that's because on how profitable it is.