Why are my brakes smoking

Might be time to clean the calipers. Brake calipers pick up a lot of dust and crud over time, more so if there are small leaks of hydraulic fluid. Don't let this problem drag on (pun intended) because if allowed to go on for a while, disk damage might result and that's a far more costly repair.

If you're brave, you can clean the calipers yourself since the calipers are relatively easy to access (just take the wheel off) and rarely require special tools. However, brakes are safety-critical, so if you do not have previous experience on the matter it might be a good idea to call in a buddy who does.

The basic procedure entails removing the caliper from its mounting bracket and pull it off the disk. Some degree of force might be required to pull off a sticky caliper, use of colorful language might help :) Take care not to nick or kink the brake line, and do not disconnect the brake line from the caliper because if you do you'll spill brake liquid (which is an excellent paint stripper!) everywhere and you'll have to purge the brake system afterwards, which is a rather tedious task.

Drop the brake pads out of the caliper, while you're at it, inspect for uneven wear that may indicate problems especially with floating calipers. Thoroughly clean the caliper, start with a brush and/or compressed air (wear a mask!) to remove the dust, then spray on some brake caliper cleaner to remove the gunk.

When the caliper is nice and clean, push the piston(s) in a bit - sometimes this can be done by hand, but most likely you'll need to use something to act as a lever. A piece of wood is preferred, since scratches on the pistons must be absolutely avoided. Have someone operate the brake pedal and inspect the movement of the pistons, when the pedal comes up the pistons should recede slightly. If not, repeat the operation a few times, with a shot of caliper cleaner in between. When you're satisfied that the pistons move freely, reassemble the caliper, maybe with fresh pads as warranted, and put everything back in place. As a final test, actuate the brake pedal a few times so the pistons and pads re-position themselves and check if the brake still drags.