Because the DCT is conceptually at odds with the way vehicles are driven on public roads.
DCTs are more successful in racing because the pattern of use is more predictable, and smooth low speed operation isn’t important.
Creeping in stop-and-go traffic, parallel parking etc, are hard on the clutches.
Wet clutches with their cooling would be a help, but the Hyundai at least uses dry clutches, and will go into a limp mode when they get too hot.
No matter how sophisticated the trans controller is it can’t always anticipate what a street driver is going to do.
This can be a minor annoyance with a conventional auto trans, but is a real problem with a DCT because it operates sequentially.
Taking the 7-speed as an example, there are two gear sets.
One is gears 1, 3, 5, 7; the other 2, 4, 6, reverse.
One of the two clutches selects one of the gear sets at any given time.
The other gear set is set up for an anticipated gear change, when one clutch releases and the other engages.
Suppose you gently accelerated up into 4th gear, then you go onto a highway ramp and punch the gas.
But the trans has set the next gear shift up for 5th gear, anticipating more gradual acceleration.
But what you really need is a downshift to 3rd.
What you get instead is limited power and delay.
Some say the problem is drivers need to adjust their driving style to suit the DCT.
But I think the vehicle should accomodate any reasonable driving style for it to be truly automatic.
I’ve been driving mostly manual cars for ~35 years and recently bought a 2017 Tucson, my first automatic since my 1985 Accord was stolen in 1993.
When I did research on the Tucson I saw that ~90% of the complaints on carcomplaints.com were related to the DCT, so I got the conventional 6-speed auto.
I don’t care that it gets 2mpg less in the city or that it’s about a second slower to 60mph.
I care more that it takes off every time I push the go pedal.