Well, you might be right, but Oracle DB brings a lot of features and is such a pleasure to use. I mean, seriously, this DB is the star of the industry right now.
With the amount of data such engines are designed for, the footprint doesn't really matter - nor does the cost most of the time, which is pretty astronomical (but SQL Server is really close). Oracle Database is clearly not recommended for home DB stuff or even small businesses (just go MySQL). There is, however, a free small-footprint version: XE (express edition). It offers a lot of features, keeps up to 11GB of data and uses up to 1GB of RAM. It can be used commercially.
Especially the 11GB is important, since SQL Server Express, which has the same purpose and very similar limitations, can hold just 10GB.