Most recordings I find are not balanced properly. I think an awful lot of mastering "engineers" are partially deaf in one ear.
If your power amplifier has L/R level controls (like most decent ones do) that does the same job.
Volume levels on power amps are typically not designed for heavy day-to-day usage. They are meant for gain staging, and they often pots on the back of the amp.
At least I hope Topping doesn't think this is a good reason to not provide a balance control.
Luckily my Auralic Vega DAC does have a balance control that works in the digital domain, but that's also not common.