"A comprehensive new study from two law students at Yale shows that routinely granting argument time to the solicitor general is a recent and curious phenomenon."

"The study asks the provocative question of whether giving the solicitor general this preferred position makes any sense. 'What we’re asking for is really for the court just to apply the same standard to all amici, whether they’re from the solicitor general’s office or not,' said Darcy Covert, who conducted the study with A.J. Wang. 'In cases where the connection to the federal government is particularly tenuous and the motivation for the solicitor general entering the case may be ideological, in those cases he certainly shouldn’t be getting oral arguments.'... Starting in 1988, though, the office’s success rate started to rise, reaching almost 100 percent. From the beginning of the term that started in 2010 through the end of the one that began in 2017, the court granted just eight of 26 motions for argument time from amici other than the solicitor general, the study found. During that same time, the court granted 252 of 253 such motions from the solicitor general."

From "The Supreme Court Has a Special ‘Friend’: The Justice Department/A new study questions the court’s practice of automatically granting argument time to the solicitor general as a 'friend of the court'" by Adam Liptak (NYT).

ADDED: The occasion for paying attention to this topic seems to be the Solicitor General's argument in an abortion case last week. The NYT article begins with a statement about that case — there were 70 amici who submitted briefs in that case but only the Solicitor General got to make an oral argument to the Justices (who may delegate reading these non-party briefs to their law clerks). Later, the article notes that the federal interest in this case about the constitutionality of a state law is "not obvious." The SG only offered to provide "the federal perspective":

The motion noted that the solicitor general’s office had taken part in arguments at the last big abortion case, during the Obama administration in 2016, but it neglected to say that it had supported abortion rights in that case. In last week’s argument, Jeffrey B. Wall, a deputy solicitor general, argued in favor of a state law restricting abortions. If he was offering “the federal perspective,” that perspective had shifted with a change in administrations.

And, I suspect, the NYT perspective on routinely granting the SG oral argument time has also shifted.

It seems to me that it's much better to routinely grant the SG's request than to base the decision on which side the SG supports.