Yeah, it comes down to trust, which Bitcoin currently is lacking compared to "hard" paper currencies like the US dollar or precious metals like gold. It could take Bitcoin years or even decades to gain similar credibility.
It also comes down to familiarity, ease of use, and functionality. Bitcoin wins on the latter, but is far behind on the other two dimensions. Paper currency and precious metals are currently far better known and easier to use, and this won't change in the near future.
Over the long run, if Bitcoin continues to gain credibility (and becomes easier to use for regular folk), I'm persuaded it can become a viable alternative to paper currency and precious metals for System D transactions.
It also comes down to familiarity, ease of use, and functionality. Bitcoin wins on the latter, but is far behind on the other two dimensions. Paper currency and precious metals are currently far better known and easier to use, and this won't change in the near future.
Over the long run, if Bitcoin continues to gain credibility (and becomes easier to use for regular folk), I'm persuaded it can become a viable alternative to paper currency and precious metals for System D transactions.