Technically speaking, the bonds are not really bought and held by the issuer but are instead cancelled immediately.
In certain cases, mainly in the high-yield debt market, there can be a substantial call premium.
Thus, the issuer has an option which it pays for by offering a higher coupon rate.
The largest market for callable bonds is that of issues from government sponsored entities.
In the U.S., mortgages are usually fixed rate, and can be prepaid early without cost, in contrast to the norms in other countries.