Sparrow is slower than most vehicles which are used by experienced MWs, including airborne ones.
You don't to be a mastermind to successfully avoid sparrow's range, not to mention if it's at least 2 MWs, chances of sparrow being shredded are big enough to spare any trouble.
Rustlers can't be properly used in SF, and partially in the rest of a map, which makes them obsolete in these areas.
Meanwhile only 1-2 sparrows spawn at Ocean Docks (LS), 1 at Naval Base (SF), 1 at Area69 (LV) with 50% chance. So, if you were to take it down somewhere far away from its original spawn, you have spare time to deal with other cops and/or restock.
And for some reason, people still forget that not only Sparrow is 10 rank only, but piloting it also takes some skill.
What is 600 HP? At 249 it's already blowing up, which means you have to deal 351 damage to it to blow it up, unless pilot is quick enough to repair it mid-air.