1. Because you will will become more flexible, which most triathletes could use more of.
Why exactly?
2. Because it works your core, which most triathletes could use more of.
Abs aren't your core, unless you topple backwards on a regular basis. Lots of other things involved which have nothing to do with the abs.
3. Because it works on your balance and coordination. Always a plus.
4. Because it is a change of pace from the daily swim, bike, run.
Which is constructive to triathletes how exactly? Maybe swimming, biking, running faster slower is the only change of pace that is required.
5. Because most triathletes could use some strength training.
Why, exactly?
6. Because it saves you time, since you can workout from home.
You can't do other short exercises from home? Like running? Or cycling?
7. Because it saves you money over a gym membership.
Why would you have a gym membership?
8. Because if you do the program, you will be in better overall shape than when you began (Flexibility, Core, Strength...)
Define "in shape". Even junkies have ripped abs. Triathletes aren't healthy/fit? Can't do stretching after a swim/bike/run?
The more I hear about the virtues of what "core" is supposed to do for people it verges on beings snake oil. Not to mention the sheer ignorance if what actually the "core" involves. And the strength argument.... oh for a dead horse.