One of the primary motivations for using a RAM disk was to not beat-up SSD's with the kind of access swap space gets.
The advantage of a hardware RAM-based drive is that it is extremely fast. When these machines were built, this was the fastest way to get data on and off a swap drive.
Today SSD's are super fast. On some machines we now have a separate dedicated 250 GB SSD for swap. If it craps out, you throw it away and pop in a new one. No worries about comingling valuable data with swap space.
Isn't it better to just have the RAM as RAM than to have the same RAM used to provide swap space on a RAM disk?