は, like the, is not always needed. Look up Kim Tae's stuff on は and が.
It should be used in formal speech though unless one is somehow referring to oneself.
If we're gonna go full colloquial 「荷物重くない？」would work
if you're going to punish people for omitting particles in other sentences that don't need them, please make it consistent for all the sentences.
Duo didn't accept it when I typed this with the kanji. I've reported it (12/26/17).
I thought it would be 「にもつはおもいいですね」
That would be a factual observation of the luggage's weight. But in this case, the negative observation is more of a musing than a fact.
What Meagan said. Also, your sentence has an extra い.
The wa is implied and unneeded here :)
The person is simply musing about the bags being heavy. They have no intention of ever HELPING with them... At least based on this tiny conversation snippet :)
If I say '荷物は重くないですか？', I simply asking the fact. If I say '荷物重くない？', I would ask 'Do you feel heavy for that baggage? (can I help you?)' More emphasizing on how they feel about the weight of the baggage.
It didn't accept it when I typed the kanji version of the sentence (including は). I've reported it. (Oct. 20, 2017)
EDIT: Still marked wrong (12/26); reported again.
Where is the kanji for "omoi" introduced other than just "showing up"?