Nowadays, very few seem to care about memory footprints, resource usage and security risks in their applications. Depending on the raw computational power of modern hardware, few care about optimization and efficiency.
Which results in bloated applications and OSs.
"Works" is just not good enough. From many viewpoints.

Why userspace sucks [2006]
Why userspace (still) sucks [2007]

To quote someone at lwn.net:
"I'm glad we have free systems -- not only is it possible to spot these
problems, it's possible for people not originally involved in the
programs to step in and fix them."

Agner Fog's optimization manuals
Magnificent resources on optization and code efficiency. Much arcane knowledge in there.

by Thanasis K at 15 Sep 2008 02:10 pm
Depends on the problem the application is trying to solve. Having dabbled into GFX programming, I can see where the speed is everything. However, for "commercial" development, most of the times speed is NOT of paramount importance, feature completeness and time to market are critical.

Also, lets not forget Knuth's words "premature optimization is the root of all evil".