Which countries are we talking about??? May be the Middle Eastern countries. Because everywhere else, like the US, Canada, China, etc, etc, the premier's are too busy dealing with executive decision making. The rest of the law makers sitting in the parliament can do their job.
A country's executive's job isn't to sit inside every session and see his people work, his job is to see his elected people PERFORM their job and create laws. Which, is passed, the Premier signs and puts them into law. While his people work, on normal days, he is out and about bringing businesses, growing the economy, growing defense, growing the GDP, the economy, education, jobs and all.