Also an engineer - I've always found this to be really disrespectful. It's not multitasking, it's ignoring the people around you. If the meeting isn't worth your undivided attention, it's better to drop the organizer a note about why you're excusing yourself from it.
Making the meeting host compete feel like they're constantly competing for your attention is just really demoralizing.
Is there possibly a middle ground? If the meeting is about a big project and I have expert knowledge on a small part of that, I will often work through the meeting but stay tuned in for parts relevant to me. Spending the whole meeting in rapt attention would likely be a waste of time, but not attending at all is bad as well.
As others have said, an upfront agenda is helpful.
Making the meeting host compete feel like they're constantly competing for your attention is just really demoralizing.