(Though even more established Google products that are not Search/Ads still never make it far past the middle)
There's an awful lot higher chance of a startup product not being a "safe" buy compared to an established company to kill a somewhat popular product and you can always look at their track record before making a decision (something a startup, by definition, typically doesn't have).
While it might not necessarily be true of 50%+ of companies that are acquired go into the deadpool, it's common enough that an acquisition of a company's product that you use should cause you at least to make sure you have some sort of strategy to deal with a potential deadpool situation. Maybe it's not a guaranteed probability, but it is indeed very likely.