At the time DVD started prolifering more and more player and TVs had full support for NTSC, PAL and SECAM, but you could still be stuck with some hardware only supporting standard and your DVDs would be black and white or scrambled on the display side.
Adding support for signals used in other regions to an analog CRT display meant adding more circuitry, so this feature was largely relegated to very high end sets and professional video monitors.
With digital flat panels, those analog signals were now being captured with an analog-to-digital converter. How to translate the sequence of numbers representing a formerly analog signal into something usable by the panel could now be defined in software, or even very compact digital hardware. This makes it more cost-effective to just produce one version of the decoder that works in all regions.
Especially as late as when the DVD came.
And the purpose of it wasn't geo-restrictions either.
Living in the SECAM region and wanting to watch US/british stuff makes it a lot more prominent issue that if you're in the PAL or NTSC area for instance.