Yes, basically.
Google has such a dominant position with 80%+ of the search market that we usually focus on Google to acquire traffic for clients. In some particular markets a ranking in Bing can be valuable. This is in markets where users are unlikely to (a) have a PC and (b) unlikely to change the default search engine, e.g. retirement planning and aged care, but even then the focus remains on the big prize: A top ranking in Google.
It is also worth noting that the sort of Search Engine Optimisation services that work for ranking in Google also works when trying to rank in most other search engines too, e.g. Bing or DuckDuckGo.