Most santoku, and certainly nakiri/usuba, knives are not good at supporting cutting styles that rely on the tip rolling smoothly on the cutting board; santoku tips tend to offer a more limited angle before the tip catches into the cutting board instead of rolling - while this seems to support the knife very firmly, it can very abruptly stop doing so, ending in an imperfect cut or even an injury.
Also, the tip of a chef (or kiritsuke) knife is well suited to doing some paring/cleaning work without having to change knives...
Blades that have a very straight edge (nakiri) have their use for thin or depth-controlled cuts (hasselback anything ;)...
It is likely that your local asian grocer will have inexpensive knives in most of the common asian shapes, these might not be Wusthof quality but they tend to be sharp and easily resharpened, and still of a far better quality than an equally priced supermarket knife - these are useful to experiment and find out what blades you like working with....
That said, most every knife shape/style is SOMETIMES useful even in a fully vegetarian or vegan kitchen - just not as often. It helps to think in terms of techniques rather than ingredients that these were intended for. For example, one could consider the deba and yanagiba pure fish knives - or useful wherever you need to separate elastic from hard (eg various fruit prep tasks), or slice something with long smooth strokes (eg various bakery tasks).