Garbage collection pauses are a huge concern with larger heap sizes. Depending on the application it may be OK to make a user wait for a second or two, but not for 30 seconds. Multitasking doesn't cause that kind of lag usually.

It's even more problematic for some types of trading systems or stream processing of sensor data, etc.

All the trends are working against garbage collection right now. Memory sizes are growing and we're moving away from batch processing for many workloads.

Most definitely - on a modern multitasking operating system your "all types of pauses" is generally only synchronous IO issues to disk or network - as long as you've got spare CPU available to your process/threads and you're sensible with your memory allocation.