A prosecutor or litigant for that matter can issue a subpoena fairly easily and there no no real burden of proof beyond the information sought being germane to the proceedings.
Search Warrants OTOH require both a Judge’s OK and probable cause, which the folks at find law define for search warrant purposes:
Probable cause to search exists when facts and circumstances known to the officer provide the basis for a reasonable person to believe that a crime was committed at the place to be searched, or that evidence of a crime exists at the location.
Search warrants must specify the place to be searched, as well as items to be seized.
I have a pet theory about Vlad Putin’s puppets in the White House. We know that Donald Trump Jr. met with the Russians to get dirt on Hillary (Like they really needed any extra help for that) and took aid and comfort from a foreign power interested in meddling in our 2016 Presidential election in the process. The way the Trumps operate, they would have taken help from the devil without a second thought. The lack of political experience shows through in spades but as they say, Ignorantia juris non excusat.
My bold prediction for 2018 is that will be the year President Trump is impeached. I also think Donald Jr. and his Bro-in-law will look good in prison orange.