For certain styles of coffee, crema in espresso is not necessarily desired — it typically has a high concentration of more bitter flavor compounds.

If you're drinking light, floral and acidic coffees, it's been relatively "trendy" recently to skim the crema off before drinking it.

I don't bother with that, but pulling two shots and removing the crema from one of them and trying them side by side is an interesting sensory experience — I'd encourage you to try, at least once!