Why should you use the imperative in the conditional if the present tense suffices?

Question

Hello,Why should you use the imperative in the conditional if the present tense suffices?In this lesson it is taught that you have to use the imperative in the conditional if you want to give advice.However, in the other lesson "Si [if] followed by present indicative + main clause (present tense/future tense)" there are also sentences that give advice without using the imperative.Si te gustan esos pendientes, deberías comprarlos.If you like those earrings, you should buy them.

Answer

Hola David
These different lessons are showing different structures used with "si", and they are the common tenses used, although we also do other combinations like using deber in the conditional with the same function: giving advice.
So, you can either say:

Si vas a Sevilla, visita la catedral 
If you go to Seville, visit the cathedral

or

Si vas a Sevilla, deberías visitar la catedral.
If you go to Seville,  you should visit the cathedral

It is simply to ways of saying the same thing. 
I'm not sure if this is what your question was about, as I'm not sure what you mean when you say: "Why should you use the imperative in the conditional if the present tense suffices?" 
Would you like to clarify a bit more?
Inma