More rational explanation IMO is that previous incurred tax...

More rational explanation IMO is that previous incurred tax losses can only be used if the majority of ownership remains at 50% plus 1 share when the nature and business structure change. If this drops below 50% then tax losses can not be used anymore. This is an anti-tax avoidance rule.
EG if company has 40M in tax losses and nature & business structure change and original ownership is reduced to 50% minus one share, the 40M tax losses are lost.
If next year 40 M profit is made, then 30 % tax will need to be paid, if tax losses are available tax will be $0, as previous losses are soaked up first.