A few situations where they may have some merit.
1) Training fasted and used prior to fasted training (which really does not make it fasted training anymore)
http://www.leangains.com/2010/04/leangains-guide.html
2) Between meals spaced 4-6 hours apart as a bolus to help maximize MPS (Muscle Protein Synthesis)
http://spotmebro.com/layne-norton-phd-on-protein-how-much-and-how-often/
http://www.slideshare.net/biolayne/optimal-protein-intake-and-meal-frequency-to-support-maximal-protein-synthesis-and-muscle-mass
Podcast:
https://www.biolayne.com/blog/news/episode-2-of-muscle-college-radio-muscle-protein-synthesis/
Protein Info:
https://www.biolayne.com/coaching/faq/part-d-protein-info/
3) Used at a meal where there is use of incomplete protein sources to help reach 3-5g leucine in a sitting to maximize MPS. Say if you had a meal of rice and beans, and needed more complete protein. Another example. You eat a cheese pizza and need more protein/bcaa's to help reach an adequate amount of leucine you would add BCAA's to that meal.
When you don't need BCAA's:
1) If your training fed.. Food is overlapping into the post-workout period, so eating a meal and then sipping on BCAA's shortly after constantly is elevating MPS, and never allowing it to reach baseline or to its refractory stages.
2) Sipping on them all day. Totally pointless, that is like eating chicken every 10 minutes.
I will quote Mr. Cooper on this one:
"Don't fall for the "it's a great replacement for sugary drinks" argument. BCAAs are 6 calories per gram, and when sipped in an all day fashion, contribute heavily to both an insulin response and gluconeogenesis. Sipping on BCAA’s takes away from MPS (Muscle Protein Synthesis) as levels never get a chance to reach refractory stages before being spiked again The net effect is increased insulin and blood sugar."
In the grand scheme of things, if you are reaching a protein requirement of 1-1.5g of protein a day, and spreading our your meals evenly (every 3-5 hours) the need for a BCAA would be minimal. Especially since most people use a whey protein powder to help reach their protein intake which has a full AA Profile (or should), but we know how companies like to cut corners in the industry.