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One reason might be to validate that the card works at all.

Another might be to bypass anti-fraud provisions of the issuer. (It seems plausible that someone trying to buy a laptop at a random retailer away from home might be less likely to trigger a fraud alert if they had a same city, same timeframe hotel reservation on the card.)

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As discussed elsewhere in these comments the booking agent will likely not be processing the payment and probably won't perform validation of the details save for a Luhn check on the number.

Someone will be attempting to process the payment.

A fraudster doesn't care who that is, any more than I care who it is when I legitimately book a hotel room.

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