D&D 5E Are certain spells considered weapons?

[Corpsetaker]

From the the PHB:

What Is a Spell?
A spell is a discrete magical effect, a single shaping
o f the magical energies that suffuse the multiverse
into a specific, limited expression. In casting a spell,
a character carefully plucks at the invisible strands of
raw m agic suffusing the world, pins them in place in a
particular pattern, sets them vibrating in a specific way,
and then releases them to unleash the desired effect—in
most cases, all in the span o f seconds.

Spells can be versatile tools, weapons, or protective
wards. They can deal damage or undo it, impose or
remove conditions (see appendix A), drain life energy
away, and restore life to the dead.

So what's to stop an Arcane Trickster from using Sneak Attack with Chill Touch or a spell that is ranged?

 

[Paraxis]

Because of game terms.

Some spells have you make a "melee spell attack" or a "ranged spell attack" but not a single one has you make a "melee weapon attack" or "ranged weapon attack", even flameblade which summons a flaming weapon isn't a "weapon" attack.

A few spells like shiraleah modify an existing weapon and buff the normal weapon attack, but that is not the same thing.

 

[famousringo]

And since Paraxis covered the how of it, I'll cover the why: Because rogues are meant to scale with with their sneak attack, while cantrips are meant to scale as if they granted extra attacks.

Arcane Tricksters would enjoy too much damage scaling. At max level, 20d6 Scorching Rays. And even more warlock multiclass cheese, if that's even possible.

I dig the flavor of backstabbing with spells, but it just wouldn't work without some serious design tweaking.