The other side assumes lip-syncing is always a deception, but that misses the point. A lot of public performances aren't about proving you can sing live—they're about the whole package: choreography, staging, lighting, the visual moment. When an artist is dancing their lungs out during a halftime show, forcing live vocals would actually make the performance worse. The audience isn't being tricked; they're watching a produced piece of entertainment, just like a music video.
And honestly, calling it "should not" is way too absolute. There are plenty of legitimate reasons to lip-sync: illness, vocal strain, technical issues in a massive venue. The real problem isn't lip-syncing itself, it's pretending otherwise. If we're upfront about it, or if the context makes it obvious, there's no harm. The fans still get the spectacle they came for. What matters is honesty about the format, not banning a useful tool.