Not valuing your time makes you less productive.
During a big part of my life, I valued hard work and considered it as a good trait, partly due to my Asian upbringing. More often than not, it caused me to waste time on stuff that wasn't so important, or that could be done faster.
I valued more the idea of hard work than the time I spent doing it.
Bill Gates famously said:
When I want something done, I'll find the laziest person to do it and task them to do it. They will find the easiest and fastest way to do it.
Being disciplined and hard-working sounds good, but when it's not used adequately, it becomes counter-productive. The problem in everyday life when you have a work hard mentality is you end up wasting time, just because you tolerate hard and menial work for the sake of it.
If you see your time as critical, you're always looking for ways to do things faster, smarter, and to spend less time on the operational stuff. Thus, the more you value your time, the more productive you seek to be. And the less you value your time, the more you'll put up with boring and tedious work, which inevitably ends up in wasted time and resources.
Sometimes work can be procrastination in disguise.
Those who can't stand wasting their time end up finding ways to reclaim it by using their wits instead of just their muscles and abnegation.