I work in software and deal with a lot of our recruiting, in turn I see this happen a lot (we are hiring our interns now since they are graduating soon). There are a few ways this can play out and I will offer some advice and reasons to why what happens happens.
First off it is perfectly normal for you to negotiate your salary. This has nothing to do with coming on from an internship or applying to a new company its just business as usual the way I see it. You can do so by simply saying something like "The offer does not meet my needs/cost of living in the area" I did this with a lot of jobs that I was offered out of college, generally the offers in cities went up significantly (but they were kind of low to begin with). These companies are trying to get a deal on you as much as you are trying to get a raise from them (don't forget that).
From my point of view you will not seem arrogant or a "not a team player" at all. The fact of life is you have expenses, rent, food, and potentially college loans which people carry in varying degrees. Your personal case may require that you make more money simply to have the job (forgetting about fun activities). Some people have the luxury of living at home after college and saving on rent, potentially not having student loans or car payments etc. These people can accept a decrease in pay as they simply don't need as much money to go about their daily life.
If you do go about it, you may get a hard No, this is nothing to worry about its just the way it is. As for why, this depends on the company. From what I have found...
Smaller companies tend to have more wiggle room in their budget as your job is often just a job in the company. The salary is not really set as much as they budget a chunk for you when they decide to make you an offer and they can often more easily move things around to offer you more (if they want you). With larger companies the jobs with in the company off fall in "Bands" or "Brackets" or what ever you like to call it. Generally these bands have salary ranges and as an entry level employee you will be hired in the lowest or second lowest level. That being said you are stuck in the salary range in that level until you get a promotion. So if you ask for more they may not be able to bump you as much as they like or at all if you are at the top of a band. This is an issue that I see all the time at the company I work for now. We are a very large company and we hire all our software engineers (entry level) in the second lowest band. The problem is that the salary range there is small (generally that band includes entry business and marketing jobs as well). Thus we cant offer the competitive tech style salaries we need to to get good talent with out hiring everyone as a manager (which we cant do)