Why are data types size limited?

I am a programmer who is mostly ignorant of database theory, and have just started using databases. From an ignorant-user standpoint, they're great except for field size limitations. Character strings must be specified as X size maximum, with a hard limit of Y characters is the longest string that can be handled, unless you use this funky other binary data type that has its own odd and difficult syntax for working with. Why is this? Why can't databases be written to handle arbitrarily long strings, and grow or shrink all input fields as needed? I don't like having to guess how long somebody's e-mail address will be, and I certainly don't like having to check every input to make sure it's not 4000+ chars. These things would be more liveable if somebody could explain why the databases are written that way, and if there is any hope of this being fixed anytime soon.

Thanks,
David

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David Eison      (404) 892-6579 x 212     <http://www.cc.gatech.edu/~eison>
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