Why are cost increases always passed on to the consumer by firms, but never cost savings?

I was watching a video about the economics of renewable energy, and one of the top comments said a major source of frustration with renewables is that policymakers and industry leaders keep championing how cheap wind and solar is, but this is never reflected in lower consumer energy bills that keep getting more expensive as the grid decarbonizes.

I read that the main reason for this in some countries like the UK is that all energy companies are required to charge at the rate of the most expensive form of energy, such as natural gas. This means that despite being much cheaper to produce, renewable energy companies cannot charge at lower prices. Apparently, this is done to prevent renewables from undercutting the rest of the energy sector and causing job losses and grid destabilization, while also creating higher profit margins that incentivize companies to invest more into renewables.

However, my concern is that by the time the grid decarbonizes years from now, there will already be a long precedent of higher profit margins thanks to the legacy of fossil fuels, so companies will not voluntarily lower prices unless forced to by regulators. This, combined with the high infrastructure costs of storage and other decarbonization expenses, means that cost savings from renewables will never be enjoyed by consumers even in a net zero economy, and energy bills will remain just as unaffordable if not worse than they are today. Is that a likely outcome?

I think you can generalize this concern to many other industries that are seeing cost saving technologies introduced, like cars, but the prices of products never actually go down.