At the risk of sounding like a broken record, a guy like Chiasson can help a team meet the veteran minimum requirement (8) for a preseason game. Maybe doesn't seem like a high number, but most teams have back-to-backs in preseason and generally a team is going to make players suit up in both. Boston has games on October 2nd+3rd. Having a guy like Chiasson saves another core player from having to make a road trip.
Edit:
For fun, here were the rosters that Boston used for a couple preseason games last year. Pastrnak, Lindholm, Carlo, and Swayman didn't dress in either game. I think fans sometimes don't realize it's standard procedure to send a junky squad for a road preseason game. Veterans in bold (a first rounder from the most recent draft also counts):
Game summary of the Boston Bruins vs. Philadelphia Flyers NHL game, final score 4-0, from October 1, 2022 on ESPN.
www.espn.com
October 1 vs. Philadelphia
LW:
Hall-Zacha-Foligno-Frederic
C:
Bergeron-Krejci-Nosek-Beecher
RW:
DeBrusk-Lysell-Wagner-McLaughlin
LD:
Forbort-Zboril-Ahcan-Wolff
RD:
Clifton-Wissmann
G:
Ullmark (played whole game)-
Kinkaid
Box score for the New Jersey Devils vs. Boston Bruins NHL game from October 3, 2022 on ESPN. Includes all goals, assists and penalty minutes stats.
www.espn.com
October 3 @ New Jersey
LW:
Frederic-Greer-Koppanen-Lauko
C:
Coyle-Nosek-Beecher-Steen-Lettieri
RW:
Smith-Studnicka-McLaughlin
LD:
Reilly-Renouf-Ahcan-Wolff
RD:
Clifton-Carrick
G:
Kinkaid (played first two periods)-Keyser