The problem with having a monetization strategy is then people can see how much money you make. If you aren't making any money and not even trying to make money, the cash investors and buyers throw at you is Monopoly money printed on valuations and total active users.
Most startups would drop in valuation significantly if they made even one penny.
Not ironic, no. It's just the truth. Do you think WhatsApp or Instagram would be worth billions if they had to make money? With the absolute minuscule amount of profit they might make, their valuation would be worth maybe hundreds of thousands. Not billions.
The reason they're valued so highly isn't because of how much money they would make, but how much value they would bring to an already profitable company. Those valuations aren't based on the idea of profits, but on the idea of being bought out by a bigger player. If they started making money on their own, that value would drop massively.
Most startups would drop in valuation significantly if they made even one penny.