Some online retailers don't give you a choice. They ship by price and service be damned.
Yup, mostly those run by MBA Accountants who only care about the bottom line and whatever bonuses that accompany that policy.
OpticsPlanet and their offshoot, DVOR, are the biggest culprits I have bought from that use DHL. Never arrives when expected, "tracking" is a joke, not a useful tool, and packaging is usually damaged when it finally does get here.
Ed