Let's say the maximum reach/exposure to voters is 100% in their country. The political establishment of many decades already have this number close to 100%, but the opposition may only have 5%. You see, the opposition has potential to gain a lot from ads, but not the establishment.
Also in a rich society like Singapore, grassroots can make huge contribution to the opposition party if their voice get heard and spread. But the establishment does not need this.
I'd argue the opposing party 5% support would likely have a matching resource pool of their size. Meaning the establishment might run 95% of all ads as ads supporting the establishment and only 5% of ads would support the opposing party. So I struggle to see how that would help the opposing party?
Obviously, it isn't that cut and dry, but America is a good example actually. Because they have 2 major parties and several third parties. But those third parties never make any meaningful growth even after running ads because they only represent >5% of the available political parties.
I'm just trying to understand how it actually helps the party in power by not allowing ads to run. Because I see the opposite situation. Honestly it seems to me both situations the sitting party has the most power, but simply due to the fact that they're the party in power.