I present the Tale of the Two-Weapon Ranger.
1E: TWF is an obscure rule. Also, the drow are described as fighting with two weapons often.
Late 1E: A drow ranger becomes a popular novel character.
2E: Rangers are two-weapon users.
The moral of the story? Blame Drizzt.
While I would love to, there's several other sources of blame, one due to Fritz Leiber, one due to Professor Tolkien, and the third is just "logic."
Leiber's Fafhrd was a dual wielder (as was the Grey Mouser). Fafhrd was also a northern barbarian skilled in the longbow, tracking, wilderness craft, and so on. Sound familiar? Although I grant he also had a pretty singing voice, and that didn't end up as a character point for Rangers.
On Weathertop, Aragorn fights off the Nazgul with "a flaming brand in either hand." Throughout the story, Aragorn, the original "fantasy Ranger" never only uses a shield when arrayed for war (Helm's Deep and similar). All the story's other "ranger" types - including Legolas, Faramir & his men, and Halbarad & the other Dunedain - carry bows or spears, and blades, but again,
no shields.
All that makes no argument for anything but rangers as archers or spearmen who also carry swords, but not shields. But this also I put forth, arguing from logic as someone who has practiced swordplay. Single-handed fighting is DUMB. Either you use your free hand to grapple, or you pick up a secondary companion weapon, as did Fafhrd. Any shield bigger than a buckler doesn't generally go with a bow.
There's also the notion that using a quarterstaff is also pretty similar to fighting with two weapons. I don't think I need to point out that one of the legendary archetypal rangers is Robin Hood. And his men, in addition to their skill with bow and sword, are famous for using quarterstaves. So, there's still more rationale.
The point is that by the time Drizzt and his dual scimitars became popular, and they were looking ahead to 3e, there was a lot of precedent for rangers as skirmishers and two-weapon fighters. So they just went ahead and made it official.
I don't deny that Drizzt was probably the impetus, but the trend was already well underway when he hit big.