Few reasons...
1) If they take few hundred K loan peg to a HDB value, then suddenly government made some cooling measures and the HDB value tanks, I am pretty sure the bank will ask them to top up via cash to offset the difference between the home's value and loan amount. If they took out a collateral loan, lagi gg. You can expect a lot of bad debts and bankruptcies.
2) Sinkies are selfish. Imagine you and your friend everyday kpkb about government and rising cost. But now your friend getting married and die die need to buy house liao... He take whatever current value there is, say, $1 million. Do you think they will be happy if suddenly a cooling measure kicks in? They will immediately become die-hard opposition supporters who wants to 'teach' the government a lesson by voting the opposition. However, if nothing much is done to cool the value and value keep going up, these people will feel they are rich and they are afraid of their home value to drop... If the opposition makes the mistake of proposing cooling measures, these voters will immediately side with the ruling party or government.
For other words, if they do any cooling measure, it will push more people to vote against the government instead. Rather take tiny measures or leave it as that and say it is 'supply and demand'. Do you think those people living in condo or landed want their value to drop? lol
I can guarantee you those who once die-die want to vote opposition but now their HDB value is near or over millions of dollars in value, they will want to keep things the way it is... They would either vote for the ruling party, or null vote. Either way, it benefits the ruling party.