Grenades can be used to flush people out from cover as well as used to try and hurt them directly.
Example: "Two-Bats" Nick, the former MLB pitcher turned Shadowrunner after his adept status was revealed, is working with "Tommy Gun" Timmy, who has a LMG set up on a bipod, and are trying to take out a group of Mafioso in Quebec City as part of a job. The Shadowrunners have good cover in a brick and mortar framed window on the second-floor of a building, while the Mafioso has gone to cover behind their armored cars. (The cars are incapacitated by GridGuide, through the work of their hacker, "Slow Hand" Luke the Technomancer.).
Two-Bats has a box of grenades of various types at his feet, and starts pitching them, bouncing them off the walls of the building behind the Mafioso and having them land under the cars so that the Mafia guys can't reach them to throw them back or kick them away. The explosion will funnel under the car into the street and sidewalk. The Mob guys freak out at the explosives that just landed next to them, and run out away from the cars, right into the sights of "Tommy Gun" Timmy.
The few that don't find out that those weren't HE Grenades, but Neurostun, and start having to deal with sleepy-sleepy hitting them, which would leave them nice and vulnerable to the street monsters that would slit a person's throat for a pair of beat up sneakers, forget the Naga Hide shoes these guys are wearing.