A) because they can, and
B) because it counts towards SWAT gear maintenance
To expand on point B, I would not be the least bit surprised if police departments' beancounters actually kept tabs on the average cost of SWAT gear maintenance costs. Higher number of conducted raids means a lower bolded number in metrics spreadsheet.
... which actually brings up another item. Do the personnel on a raid get paid dangerous duty bonuses?
I don't think the article said it was a SWAT team conducting the raid.
I mean, I could see some off-hand justification by saying that they get to practice for real raids in an unfamiliar situation... but raids are prone to inciting over-reactions and media attention, which clearly doesn't provide long term value.
Part of why the militarization of the police is so scary is because most of that equipment is given under a "use it or lose it" clause. So they have to use their tanks, otherwise the federal government will take them back.
So, they have to find "reasons" to use them even if they aren't necessary. Maybe one day in the far future they might be useful, but in the meantime they're basically toys.
