A family of Microsoft relational database management systems designed for ease of use.
If you only display data on forms and reports, you can probably (haven't tried it) set the Format property of the default text box, either in the current database, or (by modifying the blank database template) for all new databases. I haven't tried this, so I can't say for sure if this is a property you can set in the defaults, but it would be a something to check.
Unfortunately, I hardly ever use either. My desire is to have a global default of 'standard' for numbers with two decimals everytime I select 'double' as the format.
I guess you're running up against the design philosphy of Access. Access is designed to give you a lot of control of format and appearance on forms and reports; datasheets not so much.
How about this: you could have a VBA procedure that goes through all the TableDefs in a database and sets the Format and DecimalPlaces properties to your desired settings for all fields of type Number/Double or Number/Single. Such a procedure would be quite easy to write. You could then run it any time you want, on any database you want.
That's not quite as good as setting a default, but you could change a lot of tables & fields in one go.