Unless your net worth is over $5,490,000 you should not have to worry about Hawaii Estate Tax and unless your net worth is over $12,920,000 you should not have to worry about Federal Estate Tax. Multiple that by 2 if you are married.
Yes, you will get the step up in basis at death but that might leave a bigger problem, assuming they die with multiple beneficiaries. Now you have more owners and it becomes even more difficult to get things done and the income the building generates becomes less meaningful.
You also might have to deal with new owners that are unreasonable or they’re unreasonable spouses who might want to give their input.
In addition, maybe the current owners want to be able to have some cash now so they can spend it on their family members today and watch them enjoy the benefits. They can’t watch them enjoy the money when they are dead.
If my kids were to inherit some real estate, it’s bad enough that they have to deal with their siblings and spouses but it becomes even more of a headache if they have to deal with their cousins and their spouses.