The angled blade gives you more reach. Reach is essential for speed and to keep the board planning. SUP style bent shafts do two things - protect one's wrists from tendinitis, and provide even more reach for a longer stroke.
Per your other question, Surftech had at one point a entry level fiberglass paddle no angle, Surftech.com You might also check Werner's new Fiji rec paddle. http://www.wernerpaddles.com/paddles/stand_up/recreational/fiji/
Touring Kayak Paddles
The Kayak Wing
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