Spelling and grammar (not to mention syntax and punctuation) are extremely useful if we want to be understood, but it's possible to get along without them.
For instance, see how you go reading the next passage:
I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg.
Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at
Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a
wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be
in the rhgit pclae. The rset can be a taotl mses and you can sitll raed
it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey
ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh? Yaeh and I
awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins can raed tihs