Some PC laptops do, sure. For example, I have seen a Dell Inspiron (1720, other models may have similar) that could take an optional ($35 or so) multimedia cable header that included a coaxial S/PDIF RCA output. This hooked up to a built-in multifunction port on the laptop and used the laptop's internal sound hardware.
There are also external sound cards that attach via USB and provide digital outputs.
HDMI can also be used for digital audio output, and is increasingly common on newer laptops.
As for PC laptops that have a toslink or RCA S/PDIF output actually built in to them (without an external cable header/adapter), that I haven't personally seen. I am not a MAC guy, so that may be something you can find on the other side of the fence.
Are any of these good solutions? That's up to you to decide, but there are quite a few ways to get digital audio out of a PC laptop.
Also, isn't the limiatation you speak of a limitation of the USB DAC, and not the PC?
