No one is forced to contribute to a 401k. If your employer offers a 401K, they can take money out of your paycheck, and the tax on that amount will be deferred until you withdraw from your 401K. If you draw out of your 401K before retirement age of 59 1/2, you will have to pay a penalty of 10% on top of the tax. Many employers that offer a 401k also include a match. Most companies match 50% of what the employee contributes. The catch is that you usually have to work for an employer for a certain amount of time before you are fully vested and can claim this portion if you leave the employer. My employer has a vesting schedule of 5 years.
There is quite a bit of latitude with employers in how they create the 401k plans - and sure there are standards in place too.
Since about the 90s, many employers have begun to provide 401ks to replace traditional pension plans... Sure there are some employers who have both traditional pension plans and a 401k plan.
The matching portion is also variable, and most employers have limits in how much they match... They might match up to a certain amount per year or they might match a certain percentage of the employees voluntary contribution.
In the early days of 401ks in the 90s, the yearly maximum contribution was something like $5k, and currently it is in the $18k per year range. There may be a few employers who will match the full $18k, but many of them are much more skimpy, if they actually have matching programs at all.
401ks are still a pretty decent investment because of both the tax deferral aspect and the employer matching, if they have such matching.