Slows down your app too, sometimes. Depends how well you can work with and mutate a DOM, but if all things equal no VDOM is always faster cause no diffing.
A lot of people can benefit from offsetting mutations with rAF and dbl rAF and batching reads/writes (FastDOM), before needing or considering a VDOM. VDOM came to prominence because of REACT and then started becoming used even when it wasn't needed. It does serve a purpose and scenario when needed, tho