Airalo, Flexiroam etc buy data volume package on trading platforms at short notice and resell it via their eSims. Hence the eSIMs are valid only for that transaction period and only for data, no phone numbers are provided as India doesn't allow it post David Headly & the Mumbai attacks. (As you may recall, the terrorists had phones with prepaid SIMs that had been purchased for them in advance)

For example if say AT&T in the US expects their users to roam for x000 000 GB in India in May 2024, they make a deal/contract with Airtel/Jio/V for that volume. When a AT&T user lands in India, the AT&T sims will link up with the provider the contract is with. Sometime during the contracted period AT&T may notice that the offtake is not what they had contracted and they see a certain volume expiring soon. They then put this up for sale and Airalo picks up a few thousand GB for peanuts.

Jio & co might not like this much and perhaps approached the DoT/Regulator to ban this practice under security pretext.