using desde with only the present tense

Question

On all the other sites that I have read, you conjugate the verb in the correct tense when using desde. Can you please clarify this for me? I read in the comments that the tendency is to use the present tense, but why do none of the other sites say this?

Inma Sánchez · Answer

Hola Kerry 
As we don't know which other resources/ sites you've seen I'm not sure, but the most natural way to say that you've done/haven't done something since (time) is by using the present tense. You may see it occasionally using the perfect tense but it's not the most general usage. 
I had a quick look at other resources that coincide with this usage (present) and here are two other examples:
source one
source two
Saludos