Isn’t it easier to use a 1000 µl micropipette tip for all volumes? I don’t understand why there are different tips for smaller volumes. Does it affect the accuracy of the pipette for very small (<5µl) samples?
The short answer is yes, the accuracy is affected.
Automatic pipettes are most accurate in the middle of their range. The average error on a pipettes is already about 2%, but this is worse at the top end or bottom end of the pipettes minimal and maximal volume.
More subtly, have you ever tried to pipette 1 uL with a 1 mL pipette? Or even 5 uL. The bore of the pipette is too wide for starters, and the expulsion force/pressure to eject the fluid wouldn’t work very well.
On top of that, the surface tension would seriously hamper any ability to actually manipulate the fluid.