Why do some towers reference departures by compass direction, others by leg of pattern?

Got my Private about 6 months ago, and I've always wondered - let's say I request a VFR departure to the South, with the active runway being, say, 2. Some towers will give my departure clearance in reference to the requested compass direction, i.e. cleared for takeoff runway 2, right turn to heading 180 approved whereas other towers will reference it to a pattern leg, such as cleared for takeoff runway 2, right downwind departure approved. Similarly, I've noticed pilots based at airports that use the latter convention will follow that convention when making their departure requests. Is there any rhyme or reason behind which convention a tower follows?

• @SentryRaven Are we sure this is in relation to FAA regs? All indications seem to suggest it, but not seeing that definitively. Am I overlooking something? Chris, are you asking from the context of operations under the FAA? – J Walters Feb 12 '16 at 13:32
• @JonathanWalters Yes, as 7 out 5 EASA CAA / countries use mandatory reporting points to enter or exit a CTR. Departures via headings or downwind departures are not commonly used here. That sounds like FAA phraseology to me, but I can be wrong there... – SentryRaven Feb 12 '16 at 13:38
• @SentryRaven It's common shorhand at some airports (my home field included), but as far as I'm aware it's not officially recognized phraseology (at least the phrase downwind departure doesn't appear in the Pilot/Controller Glossary - I didn't look at the ATC Phraseology order though). – voretaq7 Feb 12 '16 at 19:19
• Maybe the OP will clarify... :) – SentryRaven Feb 12 '16 at 19:20
• Ah yes, apologies for not clarifying. Looking for an answer under FAA regs, or at least in the context of the US. I asked my old CFI and she said that sometimes a new controller will use a different phrasing than is common at the airport, so it may be as simple as "that's how it's always been done around here", but I'm curious to know if it's more formal than that – Chris Feb 13 '16 at 5:37