lag due to playing a sound is more likely a software/driver issue than a hardware one. (ADD: at least as far as the HW doesn't deal with this issue in the first place...).
The crappy embedded chips we have now are complete shit compared to what we had in the 90s. They pick up interference from everything else in your rig, and they often chug on simple tasks.
A significant cause of android's keyboard lag is the crappy chip trying to replay the typing sound over and over.
Lots of lag with embedded chips comes from waiting for sound data to be moved around and play. When the chips can't keep up you get stuttering, popping, or dropped frames.
My almost 30 old SoundBlaster 16 is laughing at this.
I wouldn't blame MS for this. Eventually it just got cheaper for OEMs to use cheap embedded parts at low or no cost than to include more expexpensive parts from other vednors. It also lets them keep the power requirements lower. The same thing happens in the GPU space. We get embedded chips and 200W PSUs.
typically the hardware does not know/understand/care about things like sound-effects or mixing, but rather just provides a looping buffer for the drivers to write premixed sample data into (typically mapped to a physical address range somewhere).
sound-chips also might offer additional features, like the ability for the drivers to set the sample-rate (and sometimes control sample-format), and adjust various volume controls (speaker output left/right volume, record gain, ...), ... (there are also sound-chips where the sample-rate and format is fixed, and volume controls are also handled in software).
(ADD: basically, hardware support for variable sample rate/format and hardware-supplied volume controls are optional features... and so depend on the specific chipset one has...).
actually, in a way, it is sort of like modems:
originally, they looked like serial-port devices, and would accept commands, and do stuff on their own, ...;
then they got reduced basically to a simplistic sound-chip connected to a phone-jack, with nearly all the "modem" stuff being done in software (AKA: winmodems).
actually, for onboard phone jacks, these may actually themselves just be hooked up to the sound-chip as well (so, there may be mono output and record buffers specific to the modem jack, ...).
practically, it doesn't seem all that bad, mostly just a person can't really expect them to do much beyond what they do already, and it may well make more sense at this point to look elsewhere (like the GPU) for advanced audio-mixing effects.