My managers at the company I'm currently contracting with are quite interested in getting me to come on full time. To this end, they keep dangling the opportunity to have paid vacation in front of me.
Vacations for software developers are interesting things. The better and more essential they are, and therefore the more justified they are in being rewarded with some vacation, the less likely it is that they will have the opportunity to do so.
The difficulty is that they're probably on a project. If they take two (or more!) weeks off in the middle of the project, they've just impacted the project plan. They could plan for after the project release, but you rarely release on time, and a late project trying to wrap up is even more hectic and personnel-critical than before, so planning for that isn't safe, either. They could plan for a reasonable period after the anticipated release, to compensate for late release, but then you're in the critical, "oh my god we've got a bug so obscure that it didn't come out in QA or UAT and no-one else can figure it out can you help, please" phase. And the reason they're having to beg is that the company has already committed them to both support for the released project and preliminary design on at least one other project.
You might say, "just take the vacation, and be damned with the company." But software developers have the most ridiculous work ethic you are ever likely to encounter. What other industry do you know in which the production team regularly works 200-250% of their paid hours in order to compensate for management ineptitude?
It's not just commitment to the work, however, but also an aversion to forcing their colleagues to work harder in order to compensate for their lack of working. Unscrupulous management (and there are many, for a number of reasons) will use this to their advantage, blackmailing programmers by their own ethics. One of the managers at my last company (after several iterations of "put in extra effort, just for the next two weeks") actually pulled the "well, if you can't work on Saturday, your colleagues will just have to work harder to make up the slack" tactic.
And that's just the developers' personal drive. Let's not even go into the whole perception of not being a "team player" thing for actually taking a vacation in the middle of a project (or not working long hours and weekends, which is why they need the vacations in the first place.)
What it comes down to is that, if paid vacation time is your biggest enticement and the means by which you distinguish yourself from other companies, you might want to have some process in place (as a joint effort between HR and project management, perhaps ... or, better yet, project management and a travel agent) that actually makes the enticement worthwhile to your team. Otherwise, your programmers are going to do the math, discover that their hourly wage is more in line with the income for delivering pizzas, and that their most significant reward is useless.