It is a nice theory to say "All employers should be providing their employees" with that kind of pension, but the reality is that it isn't feasible UNLESS you have a guaranteed customer base ad infinitum... and that only exists in the public sector where your "customers" are required, through threat of jail time, to remain customers.

Private sector companies, no matter how well managed the company and/or the pension fund for that company, can't take on the risk associated with extremely generous defined benefit pensions because they can't guarantee that they will continue to have customers into the future.  For this reason their pensions are also governed under different rules than public sector companies.

There are some changes that the government could make to pension legislation to help this, but at the end of the day defined benefit pensions really aren't viable any time customers have free will to choose  what goods or services they want.