It's not as if bitcoin was free either … There's transaction fees, the exchange's margin, and the local broker's margin (because yes, many of these people can't just use an exchange by themselves to cash-out their bitcoins).
Also, I'd be curious if you had source about the “every day” part, because I find it pretty unlikely, since it's costly, time consuming (the cheapest way to send money is going in physical stores), and people aren't usually earning money every day …
I don’t know anyone who sends remittances daily. Most send a portion of their paycheck so weekly or biweekly. And many people I know batch those payments to reduce fees so they send monthly.
The problem is that sending in Bitcoin is more expensive than WU.
Do you see the problem or not?