Scenario
In a past project you collected and analysed this amazing dataset and you stored it proudly on a disk, hard drive, a CD, an USB stick, SSD and diligently transferred it to a new medium every time you moved on, technologically and with your life. Now you are at that point in your research, where it makes sense to look at that data again. You whip out your trusty storage medium of choice, just to discover the application you had used to write and read the data has gone the way of the dodo: It went extinct and the last specimen went up in flames.1
The file is now a digital object of curiosity and not a usable research object.
Solution
Standardized formats and in particular open standards have a better change to remain readable than application specific formats.
Some areas of research have established exchange formats. Since these formats are read by more than one software, they might be a good option, but make sure that the exchange formats support all features you use in your work.
If you are uncertain what file format to store your data in, do some research, ask a colleague or two, ask you friendly local research data management staff, contact an infrastructure provider for your field of expertise.
1Just as the burning of the last dodo specimen, this is clearly a myth. The last instance of this program did not fall victim to the flames, but to the planned obsolescence of the device it was stored on.