Both previous replies include good information, so I won't rehash it too much. Instead, I'll focus on the last question in your post which is what the value of a lead is.
Whenever I'm helping a company with an implementation, the question of what a lead is good for often comes up. I usually describe it with the following scenario.
Let's say you are working a booth at a trade fair, representing a company that installs Stadium Lighting. During the fair, you have 50 people who come up to your table and give you their information and state that they are interested in buying your product and having lights installed. It might be tempting to just chuck all of them into your CRM application as contacts, but do we know for sure that they are all "worth" being in there? If you think of CRM as not just the listing of current customers, but also potential customers, you want to make sure you have a clean and curated database from which to work.
This is where leads come in. Leads allow you to import all of these people from the trade show and work on "Qualifying" them, basically vetting if they should be added to your Contact/Account table. During this vetting process (which can include phone calls, emails, other follow-up), you might discover a few things.
- 15 of the people who you spoke to thought you installed outdoor residential lighting, not stadium lights. They will never be someone who would be able to afford or utilize your company services. These leads would be disqualified and not worth creating contacts
- 20 of the people don't actually have any authority or ability to authorize installing new stadium lights at their facilities, but they do work places that have stadiums! That's great, and while there isn't a current potential sale worth creating an Opportunity for, it would still be worth qualifying this lead to an Account/Contact so you can keep in touch with them or pull their records for marketing purposes
- The remaining 15 people have active projects where they need new stadium lighting
- 5 of them are from companies or facilities that already exist in your CRM as an Account, so you convert the lead to an Opportunity and link it to the existing Account record
- The remaining 10 are new to you, so you qualify the lead and in the process create a new Contact, a new Account, and an Opportunity to continue to pursue the sale
Moving to a CRM platform really requires a clear set of definitions for your business and rules around what should be entered and when. Having well defined metrics prior to the implementation are very helpful. For example, knowing that you want to convert 25% of leads to Opportunities can be a metric to determine the quality of your marketing or outreach efforts. If you fall below this line, maybe you need to reevaluate what trade shows you are attending or the outreach channels you are using.
At the end of the day, it doesn't "hurt" to add them as a new contact, but you do lose a lot of potential reporting/data cleanliness by doing so. Ultimately, it is up to each company to decide the best approach. Nobody from outside your company will ever "require" you to use leads, but many of us will certainly advocate for their usage based on prior experience.
Sorry for the wall of text. Hope this helps, and good luck with the implementation!