Because they trust them, they know the building, they're insured, and they price competitively. Most strata managers maintain a panel of vetted contractors. It's not a kickback if the rates are competitive and you can audit them.
It's reasonable to ask the manager: do you receive any commission, rebate or referral fee from your panel contractors? Modern, owner-friendly managers don't, and will say so in writing. If you suspect inflated pricing, ask the committee to commission an independent quote on a single job as a benchmark.
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