Web Developer should not worried much about the older browser and modern browser. If people want to visit today's website without any problem, they should upgrade their browsers.

Some people can't. Take corporate environments such as banks, they have software policies that take years to implement and validating software risk is one of them - it's the same reason NASA used old 386/486 machines with space shuttle because they knew how they operate. For some places upgrading browser software isn't a high priority so backwards compatible software is always required. Having said that I do think that there isn't any excuse for home users, they should be on the latest and greatest if they want to get the best outta the software.

@bluescreen thanks for the info about corporate environments

Many are still using i.e. 8. We check our Google analytics. Management will say forget about those laggards until a hospital ceo complains and forwards the email to the person with the power to fire everybody. Meaning the devs have a "mission critical" bug to deploy to production "asap". Remember when the devs tried to say no to the feature that does not play well with older browsers but the pm wanted to make give the managers a "value added" feature. Now devs it is your mistake to fix.

Unfortunately as a dev where I work, we have to make sure our product can be accessible and viewable - whether their on IE, Chrome, Firefox, or Safari.. It's just best so return can be capitalized.

I think blaming the user is a bit outdated. "Dumb users... Can't even understand how my app works" doesn't cut it anymore. If it is hard to understand your software, users leave and you're the one left with a failed product.

That said, clients/stakeholders/managers should understand it's not really feasible to get everything running smoothly on every platform all the time. Cross-browser and cross-platform compatibility shouldn't be thrown around like it's given. It's a distinct feature that needs proper time to be developed.