There's no one answer to this question as it can vary greatly depending on the startup, the industry, the timing, and a host of other factors. That said, a recent report from Pitchbook found that in 2018, 22.2% of US startups that raised venture capital did so through a seed round. So while it's far from a guarantee, securing seed funding is certainly not unheard of.
Of course, even if a startup does manage to get seed funding, that doesn't mean they'll be automatically successful. According to CB Insights, only about 1 in 10 startups make it to the "growth" stage, where they're able to raise more significant rounds of funding. So even with seed funding in hand, the odds are still stacked against most startups.