Is there a reason I should not sign up for several credit cards?

I am 24, make about $40k before overtime and just recently started building my credit on my own.

Background on my credit:My parents helped me build a little bit of credit on my car loan from age 20-22, but I have since sold that car for a more economical option, but still have car payments (just 1/3 of what they used to be). I have been officially self-sustaining for only about 9 months, but my landlord is a friend-of-a-friend and by no means an official entity so I am certain my paying rent on time does not reflect in my credit score at all. About 6 months ago I got my first credit card. This is after being told all my life by my father (who can't control himself) to never get a credit card. I do not spend money I don't have (except the car loan) and have no student debt. I pay off my credit card several times within the month. I use it for almost everything to rack up points (I got $200 of gift cards for people for free at Christmas time!) but pay it off anytime it gets around/close to $200. I believe I started off with a credit limit of $1,500 but Chase bumped it up to $2,500 about 3 months ago.

I keep getting Chase Slate offers in the mail and finally caved today. I do not intend to use a single dollar of my $4,300 limit, but instead got it for the free monthly credit score report and to lower my credit usage ratio.

In doing that, however, I began to wonder if there is any reason I should not sign up for several credit cards to lower that ratio even further and improve my credit? If they get stolen that could be a problem, but since most companies have very forgiving policies in regards to theft, I'm not really concerned about that. The only thing I can see is having a huge amount of potential credit, that I would never use, which would make my credit usage percent/ratio very low. So, are there any disadvantages to having several credit cards?