Itch is a company located in the USA, so they can charge for your games and then legally give you that money. These transactions must be reported to the US tax authority (the IRS), and to do so, you must be identified by completing the interview.

So, it's not a whim of Itch, but rather a legal step you must take to be able to use Itch or any other company located in the USA. If you want to sell on Steam, for example, you must also go through a similar process.

A couple of things you should be clear about:

The interview isn't validated by Itch; rather, it's a third-party company specialized in the subject. If I recall correctly, it's the same company that validates the interviews if you sell on Steam.

Validating the interview costs $3, which is deducted from your first withdrawal. So, even if you complete the interview today, it typically won't be validated before you request your first withdrawal.

If someone in the US buys your game, the government requires Itch to withhold 30% of that sale as taxes. Depending on the country you live in, this percentage may be lower, even 0%, but it depends on the treaties between your country of residence and the US.

I don't remember the exact questions, but basically it's your country of residence, full legal name, legal address, and usually the tax identification number you use in your country.

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The other alternative is for you to sell directly, in which case you would be a company selling from your country. This avoids the interview, but you, as a company, are responsible for managing all applicable taxes.