Does it make sense to park non emergency funds like wedding, travel, reno costs in S&P500 index funds like SPY or VOO?

Yes, S&P500 trending up, but it dont go up in straight line. At least more than 5years, has a better probability to profit. Eg. U bought in 2018 , u marry at 2020. U loss $$$. Never know when is a correction.

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Tbh, I wouldn't advise it. For such investments to pan out well, usually it takes a long time horizon which usually is advised as more than 5 years. That said, I do think 5 years does expose yourself to certain risks such as the risk of a lost decade (see 2000s, 1929-1940 etc).

I would advise lower risk vehicles instead, perhaps high yield accounts, cash management accounts etc. Your returns will be less but I think you'll find that you sleep much better at night.