I think some on here are not taking into account that not everyone is a good driver, not everyone is a fast driver, others are anxious / nervous drivers, some are not regular motorway drivers so would not be very experienced driving on them. But they are all entitled to use the motorways and lay-bys.
The powers that be rightly provide proper slip roads with 300 metre merging lanes so all driver types and vehicles can join the motorway safely from junctions. But they only provide short and narrow 80 metre merging lanes from lay-bys. That makes no sense to me. Yes some will merge safely in 80 metres but many won't be able to.
I would not be against lay-bys if there were proper length merging lanes, and a properly barrier to prevent any out of control vehicle ploughing into those in the lay-by.