On a real piano, tuners can tune the top end sharp and the low end flat. This tuning technique known as "stretch tuning" gives a bigger sound to the instrument - although it can muddy the sound too much.
On a real piano, when you depress the damper pedal, with sympathetic resonance, you ring many more notes than you play - thus giving you the 'bloom' of the piano with the pedal down. The stretch tuning rings the slightly out of tune sharp treble and flat bass notes. Much like detuning two synth osilators you get a bigger sound.
On a sampled piano, there is no sympathetic resonance, so the benefits of stretch tuning are limited to sharp treble and flat bass only when you actually play the top and bottom end.