Vinyls have even harmonics which add to a smooth, natural sound. If the vinyls were digitized with a high quality ADC then those harmonics will be present in the digital version. Tube equipment also produces even harmonics so is often more pleasing than solid state. Some people, especially those who few up with solid state equipment and high levels of compression, find that those even harmonics make the sound soft.
Electric guitars produce odd harmonics which is why the sound usually has an edge to it. By comparison string instruments produce even harmonics.
And, as many have noted, the lack of dynamic compression will lead to a much more natural sound.