When is it OK for connectors to be SMT instead of TH?
The choice of through-hole versus surface-mount comes down to you, the designer of the PCB. To make that choice, you have to consider things like:


Assembly and tooling. Does the company or person assembling the PCB have the necessary tooling for the desired form factor?
Device construction and clearance. Does the device ultimately need to be space-saving? Are through-hole leads going to cause clearance problems in a restricted form factor? Is there another PCB or something nearby which through-hole leads and the resulting solder could be too close to?
Strain/durability. Is the DC jack going to be regularly exposed to physical wear and tear? Are users going to be plugging and unplugging the device often? Through-hole may afford some additional strain resistance and durability.
Cost. If you're building 100k units, a small difference in cost between the TH and SMT version of this component might matter.