If you’re recreating issues on the desktop, then you can’t be certain that any of your fixes will work. To put it bluntly, these hacks don’t work.
For instance, a developer might shrink the size of the desktop browser’s window to test a responsive website or alter the user agent to spoof a particular mobile device. In general, these hacks were an attempt to recreate a given issue in a desktop browser and then debug with Chrome Developer Tools or a similar desktop toolkit. With a distinct lack of debugging tools, developers turned to a variety of hacks.
Sure, you could get ahold of a device and perform a quick visual assessment, but what would you do after discovering a bug?
In the early days of mobile, debugging was quite a challenge.
