Why 30-month wait to purchase a second EC?

My spouse and I are the owners of a three-bedroom Executive Condominium (EC). I am interested in a new EC development that offers four- and five-bedroom units to cater to the needs of my growing children.

To my dismay, I found out that I would have to first sell my current EC and wait for 30 months before I can apply for an EC from a developer.

If I had wanted to downgrade to a Housing and Development Board (HDB) flat, purchased directly from the HDB, the same condition would apply.

For some EC projects, depending on their completion dates, a resale levy would be payable for second-time applicants.

Could the HDB enlighten me as to why a 30-month period is imposed if, as Singapore citizens, we are eligible to purchase a flat directly from the HDB or an EC directly from the developer twice?

This is making it difficult for families with growing needs, or those who wish to downgrade for whatever reason, to purchase a second HDB flat or an EC.

Besides the 30-month period, there is still the resale levy to reckon with, if one chooses to buy a second EC.