The simple answer is no – search engine submission isn’t necessary. The majority of search engines nowadays (most notably Google) crawl and index pages by following links. Using that logic, a single inbound link from any already-indexed page will identify your page to the engine. Subsequently, if that page links to other pages within your site, they will also be indexed… and so on.
For this reason, inbound linking is very important. In fact, acquiring back-links may be the most important of SEO. In theory though, a website owner shouldn’t have to ’scout’ or ‘hunt’ for links. If the presented content is of interest, useful, and/or important, there is a natural tendency among web users to link to information. This is the basis for the Google PageRank algorithm.
With all due respect, submitting your site to the search engines can’t hurt. Plus, it only entails about 5 minutes of added work assuming you only submit to the big guys. And once is enough… you don’t need to submit your site more than once. It doesn’t help or get your site crawled any quicker or more often.
SEO is not an exact science. This becomes apparent when trying to incorporate both SEO and branding into a strategy. This process is finicky to say the least. On the one side, SEO deals with the placement of keywords and phrases. On the other side, branding deals with company loyalty and culture. Incorporating both sides dilutes the prominence of both. But eliminating one or the other may not meet all strategic and marketing goals.
Once again, it should be emphasized that SEO is a series of guidelines rather than an exact science. Having said that, the following recommendation can be used to satisfy both sides of the equation. In general, keywords and phrases (i.e. SEO) should remain the focus of any early-stage company, while the incorporation of company branding should appear later in the evolution. This is simply a general statement and should not be taken word for word.