The reason why this is the case in the UK is because we have two different parties and an election, and we have ended up with the same result.
The reason why people think it is a slippery slop is because it is. Government shouldn't have any of these powers. In the UK, it has been proven over many years that this power cannot be wielded effectively by people working for government or oversight provided by elected officials.
As an example, the OSA...no-one needs this. You may not be aware but there is a massive issue with parenting in the UK. Children are turning up to school at 4 years old unable to communicate with adults (with no learning difficulties) or use the toilet. There is a very strong belief amongst civil servants (not ministers, they are basically irrelevant) that the state must step in to perform parenting functions. Does this sound like a good idea? This is the justification in many of these areas, Ofcom use to be a small agency that regulated what commercials could run on TV, it is now grown into Newspeak regulator...this isn't over 20 years, this has happened within the last three years.