Additionally, pushover bosses won't stand up for you when Scope creep starts to happen. Before long you will have 20 new change requirements to do in the last few days because someone decided they like the old-old way. (ie the code you just tore apart to appease their previous request)

What's worse is having a boss that's a pushover in one direction. From above, it's always whatever upper management wants, and to his team, it's do it now or you're fired.

You want someone who makes you justify your estimates, so you don't run wild, but is also willing to be like "yeah that really is gonna take 3 weeks longer, go do good work, I'll get you the cover".