MySQL vs. basic text file

often i use text files at my data sources, delimted by the "|" symbol. i simply delimit the fields of each line, then when i need to open them, i open the text file, populate an array with each line, then explode the fields for each to get the corresponding values. i use this method for catalogs - and even backend interfaces, for which the client can add/edit/delete products. everything seems to be working fine, and there doesn't seem to be a need for MySQL or anything. i was wondering if there is anything i'm not thinking of that perhaps would push me to favor using php and mysql instead of the plain old text file.