A bond ETF is just a bond ladder, with many rungs, and someone else manages it for the outrageous fee of 0.09%. Yes if you hold a bond until maturity it pays its face value. But if you need to sell it before maturity it can lose capital. A bond ETF will return your invested value if you hold it for the fund's duration, because that is the point where the interest payments will equal or exceed any capital loss.I wish to point out that you probably mean bond funds, and not bonds. A maturing bond ladder does not lose equity except in a default situation and they pay a damn sight more than a bond fund without anyone absorbing the already low interest income.
A bond ladder is good for someone that wants guaranteed maturities on a fixed schedule, similar to a GIC ladder, except the GIC ladder should have a liquidity premium. A bond ETF is good for investors that want liquidity and flexibility to buy or sell smaller quantities as needed. That's why I hold both. Horses for courses.