At this point a decision to pivot may be made, along with minor tweaking. It all relates to the metric being measured, which is usually $$$ or userbase. No traction = no future.
we fail every day, maybe every hour. If you realize you're failing, that actually translates to you being aware enough to know what's going wrong.
By knowing what's wrong, you can fix it. If you're totally dedicated and obsessed, failure is just part of the process.
Failure also happens often, there's just one massive failure at the end which is basically representative of an individual who has finally found an excuse to quit something they're not totally in love with.
Startups end as a failure because the founders choose to see it that way. There's no other concrete reason why.